Flood Damage Mitigation: Report

Working Group

Principal Investigator : Parthasarathi Choudhury Professor, Department of Civil Engineering NIT Silchar, Silchar, Assam Email: [email protected]

Team members : P.J. Roy, Assistant Professor, Department of Civil Engineering, NIT Silchar, Assam : J. Nongthombam, PhD student : Ms. N.Ullah, PhD student : Ms. Arti Devi, PhD student : Ms. S. Debbarman, PhD student

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Flood Damage Mitigation: Report List of Figures:

Figure No Description Page no 1.1 Ariel map of the study area 2.1 Main River Borak from Lakhipur to Bhanga (upto Bangladesh Border) 2.2 Section Details of Barak River upto 500m countryside 2.3 Jiri Water shed 2.4 Cross sectional details of river Jiri 2.5 Ciri Water shed 2.6 Cross sectional details of river Ciri 2.7 Sonai Water shed 2.8 Cross sectional details of river Sonai 2.9 Badri Water shed 2.10 Cross sectional details of river Badri 2.11 Madhura Water shed 2.12 Cross sectional details of river Madhura 2.13 Jatinga Water shed 2.14 Cross sectional details of river Jatinga 2.15 Gagra Water shed 2.16 Cross sectional details of river Gagra 2.17 katakhal Water shed 2.18 Cross sectional details of river katakhal 2.19 Longai Water shed 2.20 Cross sectional details of river Longai 3.1 Grid Points Covering the Study Area 4.1 Flow chart for GIS application. 4.2 Digital Elevation Model of Jiri sub basin 4.3 Digital Elevation Model of Chiri sub basin 4.4 Digital Elevation Model of Madhura sub basin 4.5 Digital Elevation Model of Ghagra sub basin 4.6 Digital Elevation Model of Jatinga sub basin 4.7 Drainage network in Jiri sub catchment 4.8 Drainage network in Chiri sub catchment 4.9 Drainage network in Madhura sub catchment 4.10 Drainage network in Ghagra sub catchment 4.11 Drainage network in Jatinga sub catchment 4.12 Flow direction in Jatinga sub catchment 4.13 Drainage network in Katakhal sub catchment 4.14 Drainage network in Sonai sub catchment 4.15 Slope map for Chiri sub catchment 4.16 Slope map for Jiri sub catchment 4.17 Slope map for Ghagra sub catchment 4.18 Slope map for Madhura sub catchment 4.19 Slope map for Jatinga sub catchment

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Flood Damage Mitigation: Report 4.20 Slope map for Katakhal sub catchment 4.21 Slope map for Sonai sub catchment 5.1 1st order watersheds for Madhura 5.2 2nd Order sub-watersheds for Madhura. 5.3 2nd Order sub-watersheds for Madhura. 5.4 3rd Order sub-watersheds for Madhura 5.5 4th Order sub-watersheds for Madhura. 5.6 5th Order sub-watersheds for Madhura. 5.7 Madhura watershed (6th Order). 5.8 1st Order sub-watersheds for Ghagra. 5.9 2nd order sub-watersheds for Ghagra. 5.10 3rd Order sub-watersheds for Ghagra 5.11 4th Order sub-watersheds for Ghagra. 5.12 5th order sub-watersheds for Ghagra. 5.13 Ghagra watershed (6th order). 5.14 Selected sub-watersheds for Madhura. 5.15 Selected sub-watersheds for Ghagra.

5.16 1 Estimation of ratios RA ,RB and RL for MSW5

5.17 2 Estimation of ratios RA ,RB and RL for MSW5 .

5.18 3 Estimation of ratios RA ,RB and RL for MSW5 .

5.19 1 Estimation of ratios RA ,RB and RL for MSW3 .

5.20 1 Estimation of ratios RA ,RB and RL forGSW5

5.21 2 Estimation of ratios RA ,RB and RL forGSW5 .

5.22 1 Estimation of ratios RA ,RB and RL forGSW4

5.23 2 Estimation of ratios RA ,RB and RL forGSW4 . 5.24 1 Estimation of ratios RA ,RB and RL forGSW3

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Flood Damage Mitigation: Report

5.25 2 Estimation of ratios RA ,RB and RL forGSW3 .

5.26 3 Figure 5.26: Estimation of ratios RA ,RB and RL for GSW3 .

5.27 4 Estimation of ratios RA ,RB and RL forGSW3 .

5.28 1 1hr UH for Madhura sub-watershed MSW5 .

5.29 2 1hr UH for Madhura sub-watershed MSW5 .

5.30 3 1hr UH for Madhura sub-watershed MSW5 .

5.31 1 1hr UH for Madhura sub-watershed MSW3 .

5.32 1 1hr UH for Ghagra sub-watershedGSW5 .

5.33 2 1hr UH for Ghagra sub-watershedGSW5 .

5.34 1 1hr UH for Ghagra sub-watershedGSW4 .

5.35 2 1hr UH for Ghagra sub-watershedGSW4 .

5.36 1 1hr UH for Ghagra sub-watershedGSW3 .

5.37 2 1hr UH for Ghagra sub-watershedGSW3 .

5.38 3 1hr UH for Ghagra sub-watershedGSW3 .

5.39 4 1hr UH for Ghagra sub-watershedGSW3 . 5.40 1hr UH for Machura watershed. 5.41 1hr UH for Ghagra watershed 5.42 1hr UH ordinates for Chiri subbasin 5.43 1hr UH ordinates for Jiri subbasin 5.44 1hr UH ordinates for Jhatinga subbasin 5.45 1hr UH ordinates for Sonai Subbasin 5.46 1hr UH ordinates for Katakhal subbasin 6.1 represents the flood event from 10th – 17th July, 2004 at BpGhat. 6.2 Represents the flood event from 19th – 29th July, 2004 at BpGhat 6.3 The flood event from 11th – 21st June, 2006 at BpGhat. 6.4 Observed and simulated discharge at Annapurnaghat (event-1)

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Flood Damage Mitigation: Report 6.5 Observed and simulated discharge at Annapurnaghat (event-2) 6.6 Observed and simulated discharge at Annapurnaghat (event-3) 6.7 Observed and simulated discharge at Badrpurghat (event-1) 6.8 Observed and simulated discharge at Badrpurghat (event-2) 6.9 Observed and simulated discharge at Badrpurghat (event-3) 6.10 Flow at Annapurnaghat: observed flow , safe flow and flow by regulating upstream ungauged catchments flows from Jiri, Chiri and Madhura 6.11 Flow at Badarpurghat: observed flow, safe flow and flow by regulating upstream ungauged catchments flows from Jiri, Chiri , Madhura, Jatinga & Ghagra 6.12 Flow at Annapurna Ghat (Event-1) including and not including effects of climate change: U/S flow regulation-all catchment 6.13 Flow at Annapurna Ghat (Event-2) including and not including effects of climate change: U/S flow regulation-all catchment 6.14 Flow at Annapurna Ghat (Event-3) including and not including effects of climate change: U/S flow regulation-all catchment 6.15 Flow at Badarpur Ghat (Event-1) including and not including effects of climate change: U/S flow regulation-all catchment 6.16 Flow at Badarpur Ghat (Event-2) including and not including effects of climate change: U/S flow regulation-all catchment 6.17 Flow at Badarpur Ghat (Event-3) including and not including effects of climate change: U/S flow regulation-all catchment 7.1 Observed Sediment Concentration & simulated sediment concentration in upper network 7.2 Sediment Concentration at AP Ghat for no sediment flow from Dholai catchments 7.3 Observed Sediment and simulated sediment discharge at AP Ghat in upper network 7.4 Sediment Discharge at Annapurnaghat for no sediment flow from from Dholai 7.5 sediment concentration for no sediment flow from Dholai 7.6 Sediment concentration for no sediment flow from Madhura, 7.7 Observed sediment concentration and concentration at BPghat for no sediment flow from Dholai and Madhura subcatchments 7.8 Sediment dischargefor no sediment flow from Matijuri 7.9 Sediment discharge for no sediment flow from Matijuri and Dholai subcatcments. 8.1 Observed, estimated and 2 hours ahead forecasts of downstream flow rates at Badarpurghat 8.2 Observed, estimated and 2 hours ahead forecasts of downstream flow top width at Badarpurghat .

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Flood Damage Mitigation: Report List of Tables:

Table No Particulars Page no 1.1 Details of Major Tributaries of River Barak in the study area 2.1 Flow area Details of Barak River system 2.2 Flow area Details of Jiri River system 2.3 Flow area Details of Ciri River system 2.4 Flow area Details of Sonai River system 2.5 Flow area Details of Badri River system 2.6 Flow area Details of Madhura River system 2.7 Flow area Details of jatinga River system 2.8 Flow area Details of Gagra River system 2.9 Flow area Details of Katakhal River system 2.10 Flow area Details of Longai River system 2.11 Details of existing embankment in the study area 2.12 Details of existing major sluice gates in Barak Valley 3.1 Rainfall gauging station in the selected Grids 3.2 Estimated T-year rainfall intensity for Barak Valley 3.3 Estimation of mean rainfall using regional mean relationship 4.1 Table-4.1 basins in the Study Area 5.1 Geomorphologic characteristics of sub watersheds of Ghagra and Madhura 5.2 Morphological parameters for the subcatchments

5.3 3 1hr UH ordinates for MSW5 .

5.4 1 1hr UH ordinates for GSW5 . 5.5 Unit Hydrograph characteristics for the sub-watersheds. 5.6 Channel characteristics and parameters. 5.7 Routing parameters for sub-watersheds. 5.8 Morphological parameters and IUH Characteristics of sub basins 5.9 1hr UH ordinates for Chiri subbasin

5.10 1hr UH ordinates for Jiri subbasin.

5.11 1hr UH ordinates for Jatinga subbasin.

5.12 1hr UH ordinates for Sonai subbasin.

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Flood Damage Mitigation: Report 5.13 1hr UH ordinates for Katakhal subbasin.

6.1 Stage-Discharge Relationships for various gauging stations: 6.2 Details of the flood Events used in the study 6.3 Estimated parameter for the upper network having outflow at Annapurnaghat 6.4 Estimated parameter for the complete River Network having outflow at Badarpurghat 6.5 Peak flow improvement at Annpurnaghat for restricting flow from single upstream catchment completely ( EVENT 1: FROM 10-JULY TO 17 JULY-2004) 6.6 Peak flow improvement at Annapurnaghat for restricting flow from two upstream catchments completely ( EVENT 1: FROM 10-JULY TO 17 JULY-2004) 6.7 Peak flow improvement at BadarpurGhatfor restricting flow from single upstream catchment completely ( EVENT 1: FROM 10-JULY TO 17 JULY-2004) 6.8 :Peak flow improvement at BadarpurGhat for restricting flow from two upstream catchments completely ( EVENT 1: FROM 10-JULY TO 17 JULY-2004 6.9 Peak flow improvement (Average) at Annpurnaghat for restricting flow from single upstream catchment completely 6.10 Peak flow improvement (Average) at Annpurnaghat for restricting flow from two upstream catchment completely) 6.11 Peak flow improvement (Average) at BadarpurGhat for restricting flow from single upstream catchment completely 6.12 Peak flow improvement (Average) at BadarpurGhat for restricting flow from two upstream catchment completely 6.13 Flood events used in the study 6.14 Percentage reduction in peak flow rates in upstream ungauged catchments required to create safe flow at Annapurnaghat 6.15 Percentage reduction in peak flow rates in upstream ungauged catchments required to create safe flow at BadarpurGhat 6.16 Regulated Peak flow rates for the ungauged catchments upstream of Annapurnaghat (upto Lakshipur) that creates safe flow at Annapurnaghat 6.17 Regulated Peak flow rates for the ungauged catchments upstream of Badarpurghat (upto Lakshipur) that creates safe flow at Badarpurghat. 6.18 Evaluation of effects of flow regulation in all upstream catchments (gauged and ungauged) on flood flow at AP. Ghat including and not including effects of climate changes 6.19 Evaluation of effects of flow regulation in all upstream catchments (gauged and ungauged) on flood flow at BP Ghat including and not including effects of climate changes 6.20 Regulated Peak flow rates for the gauged and ungauged catchments upstream of Annapurnaghat (upto Lakshipur)

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Flood Damage Mitigation: Report including and not including effects of climate change that creates safe flow at Annapurnaghat 6.21 Regulated Peak flow rates for the gauged and ungauged catchments upstream of Badarpurghat (upto Lakshipur) including and not including effects of climate change that creates safe flow at Badarpurghat 7.1 Model Parameters for Upper Network 7.2 Model parameters for complete River system

7.3 Impact sediment flow from upstream catchments at Badarpurghat

7.4 Impact sediment flow from upstream catchments at Annapurnaghat

8.1 Hybrid multiple inflows Muskingum model performances

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Flood Damage Mitigation: Report

FLOOD DAMAGE MITIGATION MEASURES FOR BARAK VALLEY IN SOUTH ASSAM INCLUDING EFFECTS OF CLIMATE CHANGE

Abstract: In the present study attempt has been made to determine the extent of flow regulations required in the upstream catchments to have safe flow at important downstream damage locations in Barak river system. There are a number of gauged and ungauged catchments in the study area and downstream flow simulation model incorporating flows from all the upstream gauged and ungauged catchments have been developed for the river system. To determine the existing flow capacity of the sections in the tributary river systems as well as in the main river the sections are surveyed at a regular interval and at all critical sections along a river course and the required channel parameters and other sectional details such as flow area, top width etc are determined/computed. Expected maximum rainfall intensity for different return periods for the study area is obtained by applying L-moment techniques for the homogeneous zone identified by applying fuzzy C-means based clustering techniques.

Three flood events considering availability of rainfall records in the study area are selected and used to conduct flood movement analysis for the river system. Stage-discharge relationships for all gauging stations are developed applying regression technique and are used to express the flow depths measured at a gauging station in terms of the discharge value. Flow contributions from the ungauged catchments are obtained by using GIUH approach. Important morphological parameters for the tributary river systems required for developing the GIUH models are derived using the DEM, stream network, slope map and data obtained by direct field measurements. The IUHs obtained for the catchments are lagged using s-curve technique to derive 1-hour unit hydrograph. Contributions from the important ungauged catchments are determined by using 1-hour unit hydrograph for the catchments and the rainfall excess for the storm events during the selected flood periods. Flow Nov- 2013: P. Choudhury-NIT Silchar, Assam8

Flood Damage Mitigation: Report contributions from the gauged and ungauged catchments are integrated using equivalent inflow for a number of upstream flows applicable to the river networks in the study area. Sediment flow simulation model for the river system are developed using the sediment concentration and sediment discharge data collected for the river system. The model is used to assess the relative contributions of the catchments in sediment load in the river reaches. Downstream flow rate and flow top width forecasting models have been developed for the river system that can be applied to forecast downstream flow conditions well in advance on the basis of upstream flow rates recorded at several upstream sections. Linear Programming model is formulated for the river networks having outflow at Annapurnaghat and Badarpurghat to determine effects of upstream flows on the downstream flows. The model is applied for two cases: (i) when upstream flows from the major ungauged catchments are regulated (ii) when flows from all upstream catchments are regulated. The effects of climate change on the flow rates are incorporated in the LP model and for the changed climatic conditions flow controls required in all major catchments upstream of the potential damage sections at Annapurnaghat and Badarpurghat are evaluated. Based on the survey works, field trips and laboratory works conducted to asses existing flow capacity of the channel systems, functioning of the sluice gates in the districts of Cachar, Karimjang and Hailakandi and status of existing embankments along the river courses etc. some observations/recommendations are forwarded that may be considered for further study and / implementation for improving overall flood condition in the valley

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Flood Damage Mitigation: Report

1.0 Introduction: The Barak river system is the second largest system in the North Eastern region of India and falls within hydro meteorological sub zone, 2c of India. The river system drains 26,193 Sq. Km in India with approximately 6562 Sq. Km from the state of Assam. The area is quite undeveloped compared to other parts of India. The main river Barak receives a large number of minor tributaries and 20 major tributaries out of which 12 are wholly in India. Flood and erosion problems in Barak valley is a major cause of concern, every year there is colossal flood losses in the valley. The GOI is considering various steps for alleviating the problem of natural disasters like flood, and landslide in this area. The main river Barak has an approximate length of 900 km out of which 532 km is in India and nearly 129 km is in the state of Assam. The valley has an average width of 25-30 km and is situated in the route of south-west monsoon. Highest annual rainfall for the valley= 4194 mm recorded at Silchar in 1989. Maximum discharge for the Barak river system= 7786.08 m3 s recorded at Badarpur in 1976. As per available records, nearly 3.50 lakh hectares of land area in the valley is flood prone and some protection against flood damages is available to 57% of the flood prone areas only. There are 26 nos of major sluice gates in the valley and approximately 738 km long embankments along the main river and its tributaries exist to help reduce the impact of flood. But, as most part of these embankments has outlived the life span the embankments develop large breaches regularly during monsoon seasons causing huge flood damages.

Some of the main factors that acting singly or in combination causes flood in the valley are:

(i) High incidence of rainfall, (ii) Deforestation in the upper catchments (iii) Inadequate natural drainage system (iii) Reduction in natural reservoirs (iv) Heavy encroachment in the riverine area (v) Large scale construction activities without proper planning

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Flood Damage Mitigation: Report To improve flood scenario reducing flood related losses in the valley it is imperative that some actions be initiated against the controllable factors mentioned above. Some of the recommendations may be construction of embankments in the existing gap positions, raising heights of the existing embankments, afforestation in the upper catchments and adoption of suitable watershed management plans to reduce sediment load in the channels. To tackle flood problems in the valley solution is to be achieved incorporating due weightage to all hydrologic and hydraulic factors effecting flood movement in the river system. A comprehensive and integrated mitigation plan should be prepared based on the hydraulic, hydrologic factors and local conditions of natural reservoirs, drainage system etc. In the present study different possible measures for mitigating flood damage in the Barak valley comprising three districts namely, Cachar, Karimganj and Hailakandi using available and generated hydrologic and hydraulic information on the study area is investigated. The study is aimed at evaluatingeffects of different sub catchments on the downstream flood scenarios at important locations, namely at Annapurnaghat and at Badrapurghat for different possible actions in the upstream catchments and river reaches. To formulate comprehensive flood damage mitigation plan investigations that need to be conducted under the study are:- examination of (i) existing flow capacity for different channels in the system, (ii) Adequacy of existing embankments and sluice gates (iii) Sediment load in the river system and erosion potential of different sub catchments and (iv) Development of an efficient tool for improved flood forecasting incorporating flow contribution from gauged and ungauged catchments in the river systemand (v) Assessment of effects of climate change on flood flow in the river system.

1.1 Study Area and Data Used

In the present report investigation works conducted for recommending suitable flood damage mitigation measures for Barak valley with the main river running from Phulertal at Lakhipur to international boarder point in Karimganj district along with study results and findings are presented. The main river

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Flood Damage Mitigation: Report reach from Lakhipur to Karimganj town receives a number of medium and small tributaries as shown in Map of the study area given in figure 1(a) and figure 1 (b). A few of the tributaries in the study area are gauged while, the rest are ungauged for which pertinent hydrologic and hydraulic information required for flow and erosion modeling are not available. Details of the major and minor tributaries joining the main river Barak from Fulertal at Lakhipur to Bangladesh border at Karimjanj district are given in Table-1. River flow and stage data for different gauging stations in the study for the period 2000-2010 are collected from CWC, Shillong. The collected stage and corresponding flow data for different river sections are used to develop stage vs discharge relationships for the gauging stations. Using recorded hourly stage/flow value for different sections downstream flow simulation models for the study area are developed. Hourly rainfall intensity records for different raining gauging stations in Barak valley are collected from RMC Guwahati. The rainfall values are used to compute runoff from the ungauged catchments during the selected storm events; annual maximum rainfall records for different stations is used to determine expected maximum rainfall intensity for different return periods in the study area. Daily sediment discharge versus water discharge data are collected from CWC Shillong for the period 2000-2010. The collected data are used to develop Sediment routing model for the river system.

1.2Watershed Data:

To accomplish the proposed investigations pertinent data for the gauged and ungauged catchments are extracted using Geographic information system

(GIS). GIS technique is utilized to develop digital elevation models (DEM), slope map, drainage maps for different sub watershed. Features and characteristics of the sub basin extracted applying GIS technique are utilized for developing rainfall-runoff model by applying Geomorphic Instantaneous Unit Hydrograph

(GIUH) technique. The DEMs are developed using Survey of India Topo Maps in

1:50000 scales obtained from SOI, Shillong office. The 1-hr unit hydrograph

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Flood Damage Mitigation: Report developed for the important ungauged catchments in the study area are used to compute direct runoff hydrograph for these catchments for a set of identified storm events during the period 2000-2010.

1.3 River Networks

The Barak river network in the study area that drains three districts in the valley: Cachar, Karimganj and Hailakandi districts is segmented into a upper network and a lower river network. The upper networkterminates at the downstream gauging station at AnnapurnaGhat in the River Barak and receives flows from the upstream ungauged sub catchments of Jiri,, Chiri , Madhura and gauged subcatchments of Dholai and Maniarkhal apart from the upstream flows gauged at Fulertal in Barak at Lakhipur. The lower network consists of the main river Barak from the upstream point at Annapurnaghat to the downstream point at Badarpurghat. The downstream flow at Badarpurghat is due to the inflow at

Annapurnaghat, flows from the ungauged subcatchments Jatinga, Ghagra and flow from the tributary Katakhal with gauging station at Matijuri. To simulate and forecast water and sediment discharge at two important downstream locations namely, Barak at AnnapurnaGhat, near Silchar town and Barak at

BadarpurGhat near Badarpur in Karimganj District water and sediment discharge simulation and forecasting models for the upper network with downstream station at AnnapurnaGhat and for the complete river network with

Badarpurghat as the downstream station are developed.

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Flood Damage Mitigation: Report Table 1.1: Details of Major Tributaries of River Barak in the study area

Confluence Name of the main River Left Bank/Right Bank Tributary (District ) Jiri Right Cachar

Chiri Right Cachar

Sonai Left Cachar

Badri Right Cachar

Madhura Right Cachar

Ghagra Left Cachar

Dhaleshwari Left Cachar

Katakhal Left Hailakandi

Jatinga Right Cachar

Longai Left Karimganj

Cachar Ghumra Right

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Flood Damage Mitigation: Report Figure 1.1:Ariel map of the study area

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Flood Damage Mitigation: Report

1.4 Objectives of the present study:

The majorobjectives of the present work are to study effectiveness of the existing flood control measures in Barak valley and to recommend suitable measures for mitigating flood damages. Following are the major objectives of the present study

(i) Assessment of existing flow capacity for different channels in the river system.

(ii) Assessment of effectiveness of existing embankments in the study area

(iii) Improvement works for lateral channels and natural reservoirs

(iv) Investigation on sediment load in the river system and erosion potential for different sub catchments. (v) Evaluation of impacts of flows from upstream catchments on downstream flood flows (vi) Development of an improved flood forecasting tool for the study area incorporating flow contribution from gauged and ungauged catchments

(vii) Evaluation of effects of climate change on flood flows in the river system.

Flow Chart depicting development of flood damage mitigation plan for the study area consisting of three districts in south Assam, Cachar, Karimgajj and Hailakandi is presented in the figure given next

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Flood Damage Mitigation: Report

1.5 Outline of the present study

To achieve the above mentioned goals following field and laboratory works have been conducted.

I) Survey of main channel Barak from Lakhipur to Bangladesh border point near Badrapur in Karimganj District and survey of all important tributary channelsystems to determine existing flow capacity and other important channel parameters. II) Study of existing embankments along the main course upto International border with Bangladesh from Lakhipur and along the major tributary river systems.

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Flood Damage Mitigation: Report

III) Development of Stage- Discharge relationship for the gauging stations in the study area. IV) Estimation of T-year rainfall intensity for the study area by applying L- moment techniques. V) Development of Slope Map, Drainage Map, Digital Elevation models for important subcatchments in the study area and extraction of geomorphologic parameters, hydraulic and channel parameters by using Geographic Information System (GIS) VI) Development of 1-hr unit hydrograph for the ungauged subcatcments in the study area VII) Development and application of flow routing modelsfor the upper network and the complete river network in the study areato simulate flood flow rates at Annapurnaghat near Silchar and Badarpurgaht near Badarpur in Karimganj district. VIII) Development and applications of sediment flow routing model to simulate downstream sediment discharge and sediment concentration at important downstream locations and assessment of relative effects of erosion from different subcatchments. IX) Formulation and applications of optimization models to assess impacts of flows from different sub catchment on downstream flood flows and to evaluate suitable control measures for protecting the important downstream locations. X) Development of flow forecasting model to forecast common downstream flows on the basis of upstream flows/ river satages. XI) Development of Climate change module to evaluate effects of climate change on flood flow in the study area and to recommend suitable control measures under the changed scenarios.

Detailed description of the studies conducted to achieve the targets is presented in the subsequent sections and subsections.

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Flood Damage Mitigation: Report

2.0 Assessment of Flow Capacity of Different Channels in the River SysteminBarak Valley

2.1 Main Channel: River Barak

To assess flow capacity of the main channel Barak from Lakhipur in Assam, India upto international border with Bangladesh various data and maps available with the department of water resources, GOA have been utilized. Digital data and images collected from NRSA are used with GIS technique to identify critical and vulnerable channel locations; to extract different morphometric and geomorphologic characteristics of the channel system such as, length, slope, areas etc and to estimate channel width at different locations. On the basis of preliminary assessment made using digital images field measurements for flow depth, cross sectional areas, flow velocity etc. have beenundertaken at the identified and other critical location to estimate existing flow capacity for the channels in the river system. The main river course from Lakhipur to Badarpurghat have been surveyed to assess channel flow capacity at an interval of 2 km approximately covering critical locations such as sharp bend, narrow widths etc. M/S M.S Survey, Hoogly, Kolkata was entrusted to job of survey works. The agency surveyed the main river course in two parts and covered the channel stretch upto international border with Bangladesh. Some representative survey details of the main river is included in the following sections and full details submitted by the agency is sent separately along with this report.

2.2 Tributary River Systems:

The important tributary channel systems that have been surveyed to estimate flow capacity and other pertinent details includes the right bank tributaries, Jiri, Chiri,Badri, Madhura and Jhatinga and the left bank tributaries Sonai, Ghagra, Katakhal and Longai. A team of technical and non technical staff from the department of Civil Engineering completed the survey works of the important tributary channel systems in the study area. Relevant section details of the

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Flood Damage Mitigation: Report tributary drainage systems such as top with, maximum flow depth, average flow area etc. at a regular interval and at all critical locationsare obtained by direct measurement and / laboratory computation. The detailed description of the tributary river system along with pertinent details is presented subsequently.

2.3 Details of Existing Embankments and Sluice Gates in the

Study Area:

The survey team traversed through the river network in the study area collected details of the existing embankments along the main river and along the tributaries. Details of existing sluice gates in the subcatchments as well as existing water bodies were also recorded /measured by the team. Distance of the existing embankments from the central axis of the river course, height of the embankment, length of the embankment etc have been measured/computed for the entire river networks.Details of the embankments along the main river course from Lakhipur to Bhanga in Karimganj district and along the tributary channels in the major sub catchments are as follows:flow areas of section along the river courses in the valley are presented in Tables 2.1 through 2.10; map of the river courses and section details are given in figures 2.1 through figures 2.20(c); Details of existing embankment along the major tributary river systems and along the main river Barak is given in Table- 2.21 and list of the existing major sluice gates in the study area is available in Table-2.12

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Table 2.1 : Flow area Details of Barak River system(Jiri Muk to Bangha ) Top Width Average Maximum Safe Flow Area Dist. Between Embankment Details (Distance from Sl. No Ch Remarks (m) Depth (m) Depth (m) (Sq.m) station central line; Height in metre) Left Bank Right Bank Left Bank Right Bank

1 0 250.00 11.842 15.818 3835.250 0.000 Nil Nil Hill Forest 2 4 261.50 16.151 23.033 3785.130 4.000 Nil Nil Forest Forest Village/hill/Pineapp 3 8 215.00 11.529 11.495 2457.930 4.000 Nil Nil Forest le garden 4 12 220.85 12.727 17.445 2787.688 4.000 Nil Nil Residential Area Residential Area D= 90.00 , 5 16 212.48 10.589 13.086 1983.738 4.000 Nil Agriculture Land Agriculture Land H = 2.50 D = 70.00 , 6 20 234.94 11.76 15.868 2682.150 4.000 Nil Paddy Land Paddy Land H = 3.00 D = 192.00 , 7 24 255.10 10.18 14.67 2544.010 4.000 Nil Paddy Land Paddy Land H = 3.20 D = 344.00 , Residential 8 28 200.86 8.729 18.803 1724.126 4.000 Nil Paddy Land H = 3.00 Area/Paddy land D= 353.00 , Hut/Residential 9 30 263.27 8.378 16.31 1859.470 2.000 Nil Paddy Land H = 2.50 Area D= 321.00 , D = 40.00 , 10 32 306.27 7.516 12.278 2199.628 2.000 Agriculture Land Agriculture Land H = 2.00 H = 2.90 D = 1 Km , D= 210.00 , 11 36 201.95 9.736 13.286 1999.194 4.000 Agriculture Land Residential Area H = 3.00 H = 3.10 D = 265.00 , D = 850.00 , 12 40 273.48 7.056 14.078 1930.570 4.000 Paddy Land/Village Agriculture Land H = 2.70 H = 3.20 D= 220.00 , D = 650.00 , 13 42 287.00 8.164 13.662 2361.694 2.000 Agriculture Land Agriculture Land H = 3.00 H = 3.10 D = 183.00 , D = 85.00 , 14 44 215.40 11.39 25.936 2332.043 2.000 Paddy Land Vill/Paddy Land H = 2.70 H = 3.20 D= 30.00 , 15 46 208.21 10.519 18.839 2291.650 2.000 Nil Residential Area Vill/Paddy Land H = 2.90 D = 1 KM , 16 50 259.93 10.871 10.871 2675.210 4.000 Nil Vill/Paddy Land Agriculture Land H = 3.20 D = 129.00 , D = 440.00 , 17 53 258.94 8.85 16.17 2237.346 3.000 Paddy Land Paddy Land H = 3.00 H = 3.10 D= 10.00 , D= 280.00 , 18 60 207.6 9.613 15.852 1998.14 7.000 Residential Area Residential Area H = 1.80 H = 3.00

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Table 2.1: Contd. (Jiri Muk to Bangha ) Embankment Details (Distance from Average Safe Flow area Dist. Between Remarks Sl. No Ch Top Width (m) Maximum Depth (m) central line; Height in metre) Depth (m) (Sq.m) station Left Bank Right Bank Left Bank Right Bank D= 40.00 , D = 192.00 , 19 66 221.65 12.596 23.087 2788.289 6.000 Village Village H = 2.90 H = 2.60 D = 4.00 , D = 560.00 , Residential Residential 20 69 190.7 13.02 25.415 2526.145 3.000 H = 2.20 H = 2.90 Area Area D= 96.00 , D= 180.00 , Paddy 21 72 254.36 8.032 12.65 2680.89 3.000 Paddy Land H = 1.50 H = 2.00 Land D = 314.00 , Residential 22 74 234.04 11.48 18.65 2676.366 2.000 Nil Paddy Land H = 2.80 Area D= 186.00 , Residential 23 77 283.14 5.564 15.037 2377.168 3.000 Nil Paddy Land H = 2.90 Area Residential Residential D = 160 km , 24 80 265.73 8.563 12.602 2218.328 3.000 Nil Area/Paddy Area/Paddy H = 3.00 land land D = 1.2 km , Paddy Vill/Paddy 25 83 235.39 10.714 14.832 2430.426 3.000 Nil H = 3.20 Land Land D = 185.00 , D = 194.00 , 26 86 243.74 8.123 13.912 2025.81 3.000 Residential Residential H = 3.30 H = 2.90 Area Area D = 28.00, D = 25.00 , 27 90 345.27 7.428 11.425 2450.537 4.000 Residential Residential H = 3.00 H =3.00 Area Area D = 360.00 , D= 48.00 , 28 97 249.17 9.896 15.139 2430.551 7.000 Paddy Residential H = 3.20 H = 2.70 Land Area D = 289.00 , 29 100 255.43 10.025 14.972 2522.875 3.000 Nil Agriculture Agriculture H = 2.90 Land/Vill Land/Vill Paddy 30 102 288.54 11.158 15.656 3265.021 2.000 Nil Nil Paddy Land Land D = 680.00 , Paddy 31 108 224.19 12.67 22.879 2753.388 6.000 Nil Paddy Land H = 3.00 Land Residential D = 110.00 , Paddy 32 110 394.04 6.572 11.317 2426.054 2.000 Nil Area/Paddy H = 2.85 Land land

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Table 2.1: Contd.(Jiri Muk to Bangha )

Average Safe Flow area Dist. Between Embankment Details (Distance from Sl. No Ch Top Width (m) Maximum Depth (m) Remarks Depth (m) (Sq.m) station central line; Height in metre)

Left Bank Right Bank Left Bank Right Bank Agriculture D = 390.00 , Paddy 33 112 224.31 9.395 13.326 2242.05 2.000 Nil Land/Paddy H = 2.50 Land land D= 12.00 , Paddy 34 115 189.26 10.346 13.243 1981.264 3.000 Nil Paddy Land H = 2.90 Land D = 65.00 , Vill/Paddy Residential 35 119 227.87 12.462 16.962 3002.5 4.000 Nil H = 1.70 Land Area Nil D = 75.00 , Residential 36 120.3 417.45 9.58 16.50 4550.40 1.30 Paddy Land H = 1.50 Area Nil Residential Residential D = 163 , 37 123 321.80 12.22 18.21 4151.87 2.70 Area Area H = 1.70

Paddy Nil Paddy Land 38 126.5 362.74 8.28 12.34 3143.27 3.50 Nil Land

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Fig. 2.2(a): Section Details of Barak River upto 500m in the countryside

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Fig. 2.2(b) : Section Details of Barak River upto 500m in the countryside Nov- 2013: P. Choudhury-NIT Silchar, Assam26

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Fig. 2.2(c) : Section Details of Barak River upto 500m in the countryside

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Flood Damage Mitigation: Report Fig. 2.2(d): Section Details of Barak River upto 500m in the countryside

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Flood Damage Mitigation: Report Fig. 2.2(e): Section Details of Barak River upto 500m in the countryside

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Fig. 2.2(f) : Section Details of Barak River upto 500m in the countryside

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Fig. 2.3: Name of the sub water shed:-Jiri, Approximate catchment Area: 1052.85 km2

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Table 2.2 :Flow area Details of Jiri River system Maximum Top width = 113.05 m

Average Top width = 55.65 m

Distance from Vertical depth (m) Maximu Embankment details Name confluence Maximum Flow area m of point with top width (Approx ) in depth( station Barak in (T) in (M) 1/6.T 2/6.T 3/6.T 4/6.T 5/6.T Sq.m R Bank L Bank m) kM(Approx) MS 1 20.00 83.20 5.40 7.50 10.80 12.60 9.50 12.60 165.11 Nil Nil MS 2 17.00 99.10 6.30 7.65 8.10 8.60 6.90 8.60 157.71 Nil Nil MS 3 14.00 78.42 8.80 10.50 10.40 8.50 6.90 10.40 161.40 Nil Nil MS 4 12.50 17.10 2.50 4.30 4.85 5.10 3.10 5.10 36.48 Nil Nil MS 5 17.50 14.40 2.90 4.80 4.10 3.70 2.40 4.80 31.56 Nil Nil MS 6 11.00 74.20 7.30 9.10 8.87 6.70 4.90 9.10 124.78 Nil Nil MS 7 10.85 14.40 2.20 4.20 5.50 5.30 3.40 5.50 36.72 Nil Nil MS 8 9.80 25.20 3.80 4.80 4.90 5.00 3.70 5.00 45.15 Nil Nil MS 9 8.80 12.50 3.00 4.00 4.60 3.50 1.90 4.60 29.30 Nil Nil MS 10 8.00 113.05 12.10 14.50 13.30 9.60 7.50 14.50 259.45 Nil Nil MS 11 5.50 22.44 2.80 4.00 5.30 4.20 2.10 5.30 36.16 Nil Nil MS 12 5.00 87.47 7.10 8.70 10.40 8.50 6.40 10.40 153.60 Nil Nil MS 13 4.00 14.40 2.00 5.00 4.80 4.00 2.70 5.00 33.24 Nil Nil MS 14 2.00 80.97 6.50 7.50 7.90 7.60 5.80 7.90 128.99 Nil Nil MS 15 0.00 97.90 10.80 14.70 16.04 13.80 10.50 16.04 262.85 Nil Nil

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Fig. 2.4 : Section Details of Jiri River system

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Fig 2.5 : Name of the sub watershed:- Ciri, Approximate catchment Area : 438.66 km2

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Flood Damage Mitigation: Report Table 2.3: Flow area Details of Ciri River system Maximum Top width = 109.50m Average Top width = 60.72 m Distance from Vertical depth (m) Maxim flow area Embankment Details Name of confluence point Maximum top um (Approx ) in station with barak in width (T) in (M) 1/6.T 2/6.T 3/6.T 4/6.T 5/6.T depth R Bank L Bank Sq.m kM(Approx) (m) MS 1 38.00 67.50 6.10 7.00 6.60 4.20 2.90 7.00 86.23 Nil Nil MS 2 37.00 29.70 2.50 3.60 6.30 7.30 6.80 7.30 57.42 Nil Nil MS 3 37.50 24.10 2.80 3.90 5.30 5.30 4.20 5.30 43.06 Nil Nil MS 4 38.00 27.40 3.60 4.80 6.20 6.00 4.20 6.20 51.81 Nil Nil MS 5 35.00 64.20 3.60 5.30 6.25 6.50 3.90 6.50 76.23 Nil Nil MS 6 32.00 53.70 5.40 6.50 7.40 4.30 3.90 7.40 78.02 Nil Nil MS 7 32.00 34.50 3.80 4.90 5.50 6.90 5.90 6.90 62.49 Nil Nil MS 8 33.00 31.40 3.10 4.30 5.10 5.50 3.60 5.50 47.33 Nil Nil MS 9 34.00 35.50 4.50 5.80 6.70 4.90 3.80 6.70 59.35 Nil Nil MS 10 29.00 70.00 3.70 5.10 6.00 6.20 4.50 6.20 82.43 Nil Nil MS 11 26.00 32.10 4.50 5.10 7.70 6.00 5.10 7.70 63.28 Nil Nil MS 12 27.00 29.50 4.70 4.90 6.60 5.30 4.20 6.60 55.48 Nil Nil MS 13 26.00 75.10 6.50 7.50 6.20 7.60 5.80 7.60 119.58 Nil Nil MS 14 23.50 26.50 3.20 4.20 5.70 3.40 2.70 5.70 39.63 Nil Nil MS 15 23.00 78.00 3.20 5.40 6.10 5.70 3.40 6.10 77.30 Nil Nil MS 16 20.00 85.50 4.60 5.70 6.80 3.90 3.40 6.80 89.80 Nil Nil MS 17 17.00 70.50 6.30 8.50 7.10 5.20 4.10 8.50 102.70 Nil Nil MS 18 14.00 63.50 5.30 6.60 5.40 4.20 3.10 6.60 76.85 Nil Nil MS 19 11.00 91.50 4.20 5.80 6.60 4.70 3.50 6.60 92.91 Nil Nil MS 20 8.00 95.50 3.20 4.50 5.80 6.20 4.60 6.20 95.08 Nil Nil MS 21 6.00 109.50 4.50 6.90 4.80 2.60 1.70 6.90 85.18 Nil Nil MS 22 4.00 91.20 3.90 5.10 6.30 5.30 4.20 6.30 94.96 Nil Nil MS 23 2.00 88.50 2.10 6.20 6.90 5.40 3.00 6.90 74.61 Nil Nil

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Flood Damage Mitigation: Report MS 24 0.00 82.30 7.50 8.70 11.20 8.90 8.10 11.20 164.59 Nil Nil

Fig 2.6: Section Details of Ciri River system

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Fig 2.7: Name of the sub watershed:- Sonai, Approximate catchment Area : 488.249 km2

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Table 2.4 : Flow area Details of Sonai River system Maximum top width = 163.20 m

Average top width = 80.22 m

Distance from flow area Name of Maximum top Vertical depth (m) Maximum Embankment Details confluence point with (Approx ) in station width (T) in(M) depth(m) barak in kM(Approx) 1/6.T 2/6.T 3/6.T 4/6.T 5/6.T Sq.M R Bank L bank D=66.25M H=1.00 MS 1 52.00 (Right side 2) 92.50 6.20 9.15 12.02 11.25 9.20 12.02 183.55 Nil M

D=166.20 M MS 2 51.00 (Right side 2) 98.40 8.30 8.90 14.35 10.10 9.50 14.35 212.66 Nil H=0.30M

D=62.75M H = MS 3 49.50 (Right side 2) 75.50 5.40 6.50 7.54 5.20 4.40 7.54 100.14 Nil 2.70M

D=520.05M D=66.55M H=0.70 MS 4 46.50 (Right side 2) 60.10 5.00 5.90 6.30 6.50 5.20 6.50 88.49 H=0.90 M

D=149.75M H=232.7M H=2.30 MS 5 43.50 (Right side 2) 59.50 4.10 6.20 9.20 9.50 7.20 9.50 105.83 H=1.00 M M

D=64.25M MS 6 40.50 (Right side 2) 61.50 5.10 7.60 9.30 4.00 2.00 9.30 78.19 D=555.75 H=1.00M H=1.20 M

D=435.75 M D=62.25M H=2.50 MS 7 37.50 (Right side 2) 52.50 5.00 5.20 7.85 5.20 3.40 7.85 73.25 H=1.40 M

D=72.35 M D=132.3M H=1.20 MS 8 34.50 (Right side 2) 68.70 7.20 8.70 6.30 3.50 2.20 8.70 90.82 H=1.50M M

D=111.25 M MS 9 31.50 (Right side 2) 60.50 5.20 5.30 8.10 5.70 4.30 8.10 86.10 Nil H=1.50

D=179.4M H=1.10 MS 10 28.50 (Right side 2) 58.80 4.00 5.20 7.70 6.40 4.90 7.70 82.21 D=83.40M H=0.70 M

D=119.25 H=3.00 D=60.75M H=1.50 MS 11 25.50 (Right side 2) 64.50 6.50 9.20 6.20 5.30 4.30 9.20 99.45 M M

MS 12 22.50 (Right side 2) 61.50 6.50 9.20 6.20 5.80 4.30 9.20 97.75 Nil D = 2KM H=2.50

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Flood Damage Mitigation: Report D=96.20 M MS 13 37.50 (Left side) 52.40 9.10 11.50 15.10 9.50 7.30 15.10 143.81 Nil H=0.90M

Table 2.4 : Sonai River system:Contd

Distance from Vertical depth (m) flow area Embankment Details Name of Maximum top Maximum confluence point with (Approx ) in station width (T) in(M) depth(m) barak in kM(Approx) 1/6.T 2/6.T 3/6.T 4/6.T 5/6.T Sq.M R Bank L bank

D=48.30 M MS 14 36.50 (Left side) 56.60 8.10 9.50 14.55 10.30 8.30 14.55 146.05 PWD RD H=0.90M

D=139.00M MS 15 35.50 (Left side) 110.00 6.90 8.80 10.10 10.20 7.50 10.20 190.20 PWD RD H=1.20 M MS 16 34.00 (Left side) 22.20 3.50 5.50 6.80 4.70 2.80 6.80 45.66 Nil Nil D=209.60 M MS 17 33.50 (Left side) 70.20 4.80 6.30 9.60 5.60 4.20 9.60 95.65 PWD RD H=0.30 M MS 18 31.70 (Left side) 25.20 2.80 5.00 6.10 4.80 3.10 6.10 44.19 Nil Nil D-128.10 M MS 19 31.50 (Left side) 91.20 6.00 7.60 10.20 7.10 4.90 10.20 132.64 D = 129.60M H=0.30 H=2.10 M

D=93.60 M D=323.1M H=1.20 MS 20 29.50 (Left side) 106.20 4.00 5.20 7.70 6.40 4.90 7.70 117.37 H=1.10 M

D-127.25 M D = 186.25M MS 21 27.50 (Left side) 82.50 7.30 8.80 10.20 5.80 4.20 10.20 128.66 H=1.20 M H=1.20M

D-62.25 M D = 129.75M H=1.30 MS 22 25.50 (Left side) 79.50 4.50 6.10 7.40 5.70 4.20 7.40 96.04 H=2.30 M M

MS 23 23.50 (Left side) 89.50 4.50 6.50 7.80 8.50 6.10 8.50 124.66 D-1 kM H=1.20 M Nil

D-77.75 M D = 2 km H= 2.50 MS 24 22.50 (Left side) 85.50 5.20 6.70 8.20 6.20 4.90 8.20 114.16 H=1.90 M M

D-581.75 M D = 144.25 M MS 25 20.50 103.50 4.80 6.50 8.90 5.90 4.50 8.90 122.81 H=0.80 M H=1.20M

D-83.25 M H= D = 66.25M H=2.10 MS 26 18.50 101.50 4.50 6.00 7.80 5.70 4.10 7.80 111.74 2.20 M M

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Flood Damage Mitigation: Report D-774 M H=2.00 D = 153.50 M H= MS 27 16.50 108.00 5.80 7.10 8.80 6.30 4.30 8.80 135.30 M 3.00

Table 2.4 : Flow area Details of Sonai River system-Contd Name of Distance from Vertical depth (m) flow area Embankment Details Maximum top Maximum confluence point with (Approx ) in station width (T) in(M) depth(m) barak in kM(Approx) 1/6.T 2/6.T 3/6.T 4/6.T 5/6.T Sq.M R Bank L bank

D = 122.50 M H= MS 28 14.50 107.10 6.10 7.20 10.10 5.70 4.80 10.10 143.28 Nil 3.00

D-150.25 M H=2.10 D = 103.25 M H= MS 29 12.50 148.50 4.10 6.20 8.30 7.10 5.70 8.30 164.48 M 2.20 m

D-48.60M H= 1.20 D = 43.10M MS 30 10.50 91.20 4.20 5.90 7.30 6.50 5.20 7.30 110.84 M H=1.50 M

D-105.55 M H= MS 31 10.5 (Right side 1) 54.10 3.70 5.90 9.50 6.40 4.80 9.50 81.92 katcha Rd 0.90 M MS 32 11.50 (Right side 1) 45.80 3.10 5.40 6.80 4.90 4.10 6.80 61.68 Nil Nil D-34.55 M H= 2.10 MS 33 12.00 (Right side 1) 50.30 3.90 5.20 7.55 5.70 4.20 7.55 70.85 Nil M

D = 82.90 M H=2.00 MS 34 12.70 (Right side 1) 51.80 5.10 6.50 7.10 4.80 3.40 7.10 73.49 Nil M

D= 209.25 M H= MS 35 8.50 106.50 5.40 6.70 8.10 7.00 5.50 8.10 140.34 PWD RD 0.90 M

D=86.45M H= 0.90 D = 167.25M H= MS 36 6.50 108.50 6.80 8.50 8.00 6.10 4.80 8.50 150.08 M 4.00 M

D= 0.00 M H= D = 157.50 M H MS 37 4.50 133.00 10.20 14.60 9.30 5.30 4.10 14.60 216.89 0.00M = 1.50 M

D= 269.10 M H= D = 289.10M MS 38 2.50 163.20 2.05 3.10 8.00 10.40 7.80 10.40 176.96 1.10 M H=1.20 M

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Flood Damage Mitigation: Report D=222.75 M H= D = 1 km H=2.00 MS 39 0.00 70.50 7.10 9.20 10.10 5.10 4.50 10.10 116.95 1.10 M M

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Flood Damage Mitigation: Report Fig 2.8(a) : Section Details of Sonai River system

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Flood Damage Mitigation: Report Fig 2.8(b) : Section Details of Sonai River system-Contd

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Fig 2.9 : Name of the sub watershed:- Badri, Approximate catchment Area : 338.66 km2

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Table 2.5: Flow area Details of Badri River system Maximum top width = 103.50 M ,Average top width = 50.08 m

Distance from Vertical depth (m) Maximu flow area Embankment Details Name of Maximum top confluence point m depth (Approx ) station with borak in width (T) in (M) 1/6.T 2/6.T 3/6.T 4/6.T 5/6.T R Bank L Bank kM(Approx) (m) in Sq.m MS 1 0.00 46.00 3.70 5.80 8.10 3.70 6.00 8.10 72.38 Nil Nil D=390M MS 2 1.00 79.60 5.20 6.05 7.70 5.50 4.10 7.70 100.19 Nil H=0.45 M D =72.00 MS 3 2.00 103.50 4.80 11.50 13.40 13.60 7.30 13.60 181.36 Nil H=4.10 D =35.75 MS 4 6.00 65.10 7.20 11.20 12.10 10.80 6.35 12.10 141.71 Nil H=1.00 D =43.60 H= MS 5 7.50 50.20 6.70 8.55 10.50 9.00 5.80 10.50 108.39 Nil 1.10 MS 6 9.00 45.50 4.40 6.02 7.20 5.30 4.00 7.20 68.89 Nil Nil

MS 7 12.00 40.50 2.90 3.95 5.10 4.50 2.40 5.10 44.99 Nil Nil

MS 8 16.00 37.10 1.20 2.00 2.92 2.55 1.80 2.92 24.22 Nil Nil

MS 9 17.00 27.30 2.15 2.90 3.20 2.65 1.93 3.20 26.78 Nil Nil

MS 10 17.00 24.60 1.96 2.41 3.30 2.60 1.60 3.30 23.92 Nil Nil

MS 11 17.00 31.50 1.75 3.10 3.60 2.42 2.07 3.60 28.27 Nil Nil

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Fig 2.10 : Section Details of Badri River system

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Fig 2.11: Name of the sub watershed:- Madhura, Approximate catchment Area : 349.43 km2

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Table 2.6 :Flow area Details of Madhura River system Maximum top width = 88.20 M, Average top width = 64.11 m Distance from Maximum Maximum flow area (Approx Name of confluence point Vertical depth (m) depth Embankment details top width (T) ) in Sq.m station with barak in (m) in (M) kM(Approx) 1/6.T 2/6.T 3/6.T 4/6.T 5/6.T R Bank L Bank

MS 1 27.00 68.50 4.20 5.20 5.00 5.10 5.50 5.50 85.97 Nil Nil MS 2 25.50 73.00 3.50 4.10 5.00 5.40 6.10 6.10 87.40 Nil Nil MS 3 24.00 71.00 3.40 4.60 5.10 5.40 6.70 6.70 89.96 Nil Nil MS 4 23.00 86.50 2.50 3.60 4.30 4.70 4.50 4.70 75.66 Nil Nil MS 5 23.00 36.10 4.10 5.30 6.10 6.20 6.30 6.30 66.49 Nil Nil MS 6 24.00 33.50 5.40 5.60 5.60 4.90 4.40 5.60 59.56 Nil Nil MS 7 21.00 78.50 5.70 6.00 6.20 6.30 6.50 6.50 116.81 Nil Nil MS 8 19.00 75.50 2.55 3.20 3.85 4.00 4.30 4.30 65.20 Nil Nil MS 9 17.00 66.40 4.00 4.90 6.30 6.50 4.90 6.50 84.65 Nil Nil MS 10 15.00 43.30 5.00 8.20 9.20 6.40 5.50 9.20 85.49 Nil Nil D = 83.00 M H = MS 11 14.00 67.00 6.40 6.70 7.15 5.50 4.30 7.15 98.44 Nil 1.50 M D = 42.00 M H = MS 12 12.00 68.50 5.10 5.30 6.65 5.20 4.90 6.65 91.38 Nil 2.00 M

D = 134.00 M H = MS 13 10.00 70.00 6.90 7.90 8.55 5.70 4.70 7.90 111.97 Nil 1.80 M

D = 68.70 M D = 107.20 M H = MS 14 8.00 67.40 6.75 7.50 8.60 7.00 6.30 8.60 119.50 H = 1.80 M 1.60 M

D =84.60 M H = MS 15 5.00 88.20 6.20 8.50 11.30 9.50 7.30 11.30 157.83 PWD RD 2.80 M

MS 16 4.00 30.50 3.30 5.30 7.00 7.70 6.10 7.70 63.89 Nil Nil D = 51.05 M D = 11.75 M H = MS 17 2.00 70.50 5.80 8.40 10.20 8.10 5.30 10.20 118.61 H = 1.80 M 3.30 M

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D = 180.75M D = 233.250 M H = MS 18 0.00 59.50 6.40 7.10 8.55 6.70 5.20 8.55 102.22 H = 2.00 M 5.70 M

Fig 2.12 : Section Details of Madhura River system

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Fig 2.13 : Name of the sub watershed:- Jatinga, Approximate catchment Area : 371.86 km2

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Table 2.7 : Flow area Details of Jatinga River system Maximum top width = 98.40 m, Average top width = 66.65 m

Distance from Vertical depth (m) Embankment details confluence Maximum flow area Name of maximum point with top width (Approx ) in station 1/6.T 2/6.T 3/6.T 4/6.T 5/6.T depth (m) R Bank L bank barak in (T) in(M) Sq.M kM(Approx) MS 1 16.00 92.50 6.20 9.15 12.02 11.25 9.20 12.02 183.55 Nil Nil MS 2 14.00 98.40 8.30 8.90 14.35 10.10 9.50 14.35 212.66 Nil Nil MS 3 12.00 75.50 5.40 6.50 7.54 5.20 4.40 7.54 100.14 Nil Nil MS 4 10.00 60.10 5.00 5.90 6.30 6.50 5.20 6.50 88.49 Nil Nil MS 5 8.00 59.50 4.10 6.20 9.20 9.50 7.20 9.50 105.83 Nil Nil MS 6 7.50 61.50 5.10 7.60 9.30 4.00 2.00 9.30 78.19 Nil Nil MS 7 6.00 52.50 5.00 5.20 7.85 5.20 3.40 7.85 73.25 Nil Nil MS 8 5.40 68.70 7.20 8.70 6.30 3.50 2.20 8.70 90.82 Nil Nil MS 9 4.50 60.50 5.20 5.30 8.10 5.70 4.30 8.10 86.10 Nil Nil MS 10 4.00 58.80 4.00 5.20 7.70 6.40 4.90 7.70 82.21 Nil Nil MS 11 2.00 64.50 6.50 9.20 6.20 5.30 4.30 9.20 99.45 Nil Nil D=105.5M D=168 M H= MS 12 1.00 61.50 6.50 9.20 6.20 5.80 4.30 9.20 97.75 H= 1.60 M 1.8M D=165M H= MS 13 0.00 52.40 9.10 11.50 15.10 9.50 7.30 15.10 143.81 Nil 1.8M

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Fig 2.14 :Section Details of Jatinga River system

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Table 2.8 : Flow area Details of Gagra River system Maximum top width = 71.00 m,

Average top width = 49.95 m

Distance from Vertical depth (m) flow area Embankment Details Name of Maximum top Maximum confluence point with (Approx ) in station width (T) in (M) 1/6.T 2/6.T 3/6.T 4/6.T 5/6.T depth (m) R bank L Bank barak in kM(Approx) Sq.m MS 1 22.00 62.50 3.90 4.50 5.20 2.70 2.20 5.20 56.57 Nil Nil MS 2 21.00 65.50 4.20 5.10 5.55 4.10 3.00 5.55 68.80 Nil Nil D= 49.00 M MS 3 19.50 68.20 4.80 6.90 9.50 6.50 5.20 9.50 102.63 Nil H= 2.10 M D= 53.10M MS 4 18.00 55.20 5.20 6.90 7.50 6.20 5.70 7.50 91.34 Nil H= 2.10 M MS 5 17.50 28.20 2.70 3.20 4.70 4.00 3.10 4.70 37.43 Nil Nil MS 6 17.00 20.50 3.90 4.50 5.20 2.70 2.20 5.20 35.22 Nil Nil D= 229.20 M MS 7 16.00 48.40 3.80 5.90 6.80 5.70 4.50 6.80 70.28 Nil H= 1.90 M MS 8 15.50 19.10 2.50 3.80 4.80 3.90 3.20 4.80 34.07 Nil

D= 535 M MS 9 14.00 71.00 4.20 5.70 7.60 4.70 3.40 7.60 80.97 Nil H= 1.70 M MS 10 13.50 18.00 3.30 4.40 4.10 3.50 3.00 4.40 33.45 Nil Nil MS 11 13.00 15.60 2.70 3.70 4.30 3.70 2.80 4.30 30.55 Nil Nil MS 12 12.50 27.50 3.00 3.20 4.00 2.70 2.50 4.00 32.40 Nil Nil MS 13 12.00 55.10 4.20 5.90 7.20 4.20 3.70 7.20 70.87 Nil Nil

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Table 2.8 : Flow area Details of Gagra River system-Contd

Distance from confluence Vertical depth (m) flow area Embankment Details Name of Maximum top width Maximum point with barak in (Approx ) in station (T) in (M) 1/6.T 2/6.T 3/6.T 4/6.T 5/6.T depth (m) R bank L Bank kM(Approx) Sq.m D= 76.50 M MS 15 8.00 71.00 4.10 6.20 7.50 5.70 4.50 7.50 89.68 Nil H= 2.10 M D= 143 .00M MS 16 6.00 66.40 4.50 5.90 6.20 5.40 4.90 6.20 87.01 Nil H= 1.70 M MS 17 4.00 52.40 6.60 7.50 8.20 6.40 5.30 8.20 96.16 Nil Nil

D= 140 .00M H= MS 18 2.00 87.50 4.70 5.80 8.20 7.10 6.10 8.20 120.95 Nil 1.50 M

D= 60.50 M H= 1.70 MS 19 0.00 60.70 5.40 7.20 7.50 6.80 5.80 7.50 99.65 Nil M

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Flood Damage Mitigation: Report Fig 2.16 (a) : Section Details of Ghagra River system

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Flood Damage Mitigation: Report Fig 2.16 (b) : Section Details of Ghagra River system-contd

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Fig 2.17 : Name of the sub watershed:- katakhal, aproximate catchment Area : 1504.68 km2

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Table 2.9 : Flow area Details of Katakhal River system Maximum top width = 151.40 m Average top width = 102.78 m Distance from Vertical depth (m) flow area Embankment Details Name of confluence point Maximum top Maximum (Approx ) in station with barak in width (T) in (M) depth (m) 1/6.T 2/6.T 3/6.T 4/6.T 5/6.T Sq.m R Bank L Bank kM(Approx) MS 1 72.00 39.00 6.70 8.00 9.10 7.30 6.00 9.10 90.08 Nil Nil MS 2 71.50 34.50 4.00 4.70 7.50 5.90 4.60 7.50 60.93 Nil Nil MS 3 71.00 40.50 7.40 10.20 11.70 7.80 6.10 11.70 104.96 Nil Nil D = 425.70m H = D = 113.70m MS 4 71.00 151.40 9.90 12.70 14.60 15.90 12.50 15.90 369.01 0.45m H = 0.30m D = 134.50m H = D = 123.50m MS 5 61.00 139.00 9.10 10.90 13.00 8.90 7.10 13.00 253.25 1.20m H = 2.00 m MS 6 63.50 37.80 5.10 6.50 8.70 7.50 5.80 8.70 79.74 Nil Nil D = 102.50m H = D = 178.00m MS 7 63.00 136.00 7.20 8.50 9.20 8.00 6.50 9.20 206.67 0.80m H = 0.45 m D = 416.50m H = D = 106.5 m MS 8 60.00 133.00 8.20 10.50 11.65 15.40 12.10 15.40 300.09 1.50m H = 1.20 m MS 9 58.00 42.40 2.70 3.80 6.20 6.80 5.20 6.80 61.51 Nil Nil D = 134.50m H = D = 194.00m MS 10 57.00 143.50 6.50 8.70 11.10 10.30 8.60 11.10 240.77 1.10 m H = 1.20 m D = 240.00 m H = D = 125.00 m MS 11 54.00 119.50 9.80 12.10 12.30 9.50 7.90 12.30 244.06 1.80 m H = 0.70 m

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D = 81.00 m H = D = 221.00 m MS 12 51.00 146.00 8.40 9.30 10.10 8.80 7.60 10.10 251.07 1.10 m H = 2.50m

Table 2.9 : Flow area Details of Katakhal River system-contd

Distance from Maximum Vertical depth (m) flow area Embankment Details Name of Maximum confluence point with top width (T) (Approx ) in station depth (m) barak in kM(Approx) in (M) 1/6.T 2/6.T 3/6.T 4/6.T 5/6.T Sq.m R Bank L Bank D = 132.00m H D = 93.00 m H = MS 13 48.00 132.50 8.40 10.00 12.70 12.80 10.20 12.80 276.38 = 1.20m 0.60 m D = 245.00m H D = 150.50m H = MS 14 45.00 151.00 5.80 7.10 8.10 6.50 5.00 8.10 179.30 = 0.70 m 1.10 m D = 303.00 m D = 74.00m H = MS 15 42.00 107.70 8.80 10.50 11.40 9.80 9.20 11.40 224.95 H = 0.50 m 1.20 m D = 65.00 m H D = 66.50 m H = MS 16 39.00 120.00 7.50 9.10 10.10 8.40 6.90 10.10 199.20 = 0.90 m 0.60 m D = 62.00 m H D = 68.00m H = MS 17 36.00 110.50 7.20 8.60 9.50 9.10 8.20 9.50 196.21 = 0.80 m 0.70 m D = 50.00 m H D = 75.00m H = MS 18 33.00 100.50 7.10 8.80 11.20 10.30 8.70 11.20 192.93 = 1.00 m 0.40 m D = 233.00m H D = 131.00m H = MS 19 30.00 125.50 6.50 7.20 11.00 12.40 10.70 14.40 241.08 = 1.00 m 1.00 m D = 90.50m H D = 67.80 m H = MS 20 27.00 111.00 6.80 8.30 9.90 8.90 7.20 9.90 183.70 = 0.90m 0.70 m D = 95.00m H D = 66.00 m H = MS 21 24.00 105.50 8.20 9.10 11.80 9.70 8.70 11.80 209.78 = 0.70m 0.30 m

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Flood Damage Mitigation: Report D = 111.00m H D = 73.20 m H = MS 22 21.00 112.00 6.20 8.10 9.00 7.50 6.10 9.00 164.00 = 0.90m 1.00m

MS 23 20.00 41.20 3.80 4.70 5.80 5.00 4.10 5.80 58.12 Nil Nil

Table 2.9 : Flow area Details of Katakhal River system-Contd

Distance from Maximum flow area Name of confluence point top width (T) Vertical depth (m) Maximum Embankment Details (Approx ) in station with barak in in (M) depth (m) Sq.m kM(Approx) 1/6.T 2/6.T 3/6.T 4/6.T 5/6.T R Bank L Bank D = 562.00m D = 100.00m H = MS 24 18.00 104.50 8.20 10.10 11.20 8.10 6.90 11.20 190.30 H = 1.20 m 0.65 m

MS 25 17.00 30.50 3.10 3.70 4.90 4.00 3.50 4.90 41.98 Nil Nil D = 71.00m D = 151.0m MS 26 15.00 115.50 8.70 10.50 10.30 11.70 9.10 10.50 236.33 H = 1.00 m H = 1.00 m D = 97.5 m D = 191.5m H = MS 27 12.00 123.00 9.80 10.70 10.80 11.50 10.40 11.50 273.05 H = 1.20 m 1.00 m D = 91.50m H = MS 28 9.00 108.00 7.80 9.30 10.60 12.80 11.40 12.80 238.20 Nil 0.90 m D = 463.50m H = MS 29 6.00 120.00 8.70 10.40 10.80 8.80 8.10 10.80 228.00 Nil 1.40m D = 160.0 m H = MS 30 3.00 104.00 8.20 9.70 10.10 8.30 7.30 10.10 190.53 Nil 1.80 m

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Fig 2.18 :Section Details of katakhal River system

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Table 2.10 : Flow area Details of Longai River system Maximum top width = 120.70 m Average top width = 61.90 m Distance from Vertical depth (m) Maximum flow area Embankment Details Name of bangladesh Maximum top depth(m) (Approx ) in station border( Latu width (T) in (M) 1/6.T 2/6.T 3/6.T 4/6.T 5/6.T Sq.m R Bank L Bank Bridge) MS 1 0.00 120.70 7.70 6.90 5.83 5.20 4.10 7.70 154.55 Nil Nil MS 2 2.00 76.80 5.20 6.95 7.20 6.30 5.33 7.20 108.29 Nil Nil MS 3 4.00 79.30 6.52 6.40 8.65 6.73 6.00 8.65 126.30 Nil Nil MS 4 6.00 75.00 4.00 4.93 7.52 7.40 6.80 7.52 107.20 Nil Nil MS 5 8.00 73.50 8.20 8.95 9.32 7.83 7.50 9.32 148.36 Nil Nil MS 6 10.00 77.55 6.80 7.92 8.70 5.88 5.30 8.70 123.20 Nil Nil MS 7 12.00 70.00 6.50 7.20 7.85 6.35 5.57 7.85 113.21 Nil Nil MS 8 14.00 66.40 6.10 6.80 6.84 7.00 6.50 7.00 111.00 Nil Nil MS 9 16.00 89.40 5.97 6.72 5.90 4.70 4.05 6.72 109.29 Nil Nil MS 10 18.00 82.00 4.85 5.80 7.03 8.92 7.80 8.92 129.94 Nil Nil MS 11 20.00 71.00 7.02 8.10 8.60 5.67 5.00 8.60 115.86 Nil Nil MS 12 22.00 69.80 8.10 9.92 9.67 4.95 4.03 9.92 119.64 Nil Nil MS 13 24.00 93.20 5.70 6.45 6.50 5.82 4.77 6.50 118.86 Nil Nil MS 14 29.00 45.50 2.92 3.80 6.52 4.95 6.94 6.94 67.93 Nil Nil MS 15 34.00 38.30 2.85 3.70 5.92 4.00 3.51 5.92 47.54 Nil Nil MS 16 39.00 42.80 3.60 4.85 5.83 4.44 3.60 5.83 55.92 Nil Nil D = 78.50 M MS 17 42.00 57.00 3.00 3.95 5.80 5.30 4.80 5.80 67.15 Nil H = 1.20 M

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Table 2.10 : Flow area Details of Longai River system-Contd Distance from Embankment Details Vertical depth (m) Maximum flow area Name of bangladesh Maximum top Name of station depth(m) (Approx ) in station border( Latu width (T) in (M) Sq.m Bridge) 1/6.T 2/6.T 3/6.T 4/6.T 1/6.T R Bank L Bank

D= 58.25 M H = D = 48.25 M H = MS 19 50.00 56.50 3.10 3.55 4.52 5.05 5.80 5.80 68.14 1.30 M 1.20 M D = 56.75M H = D = 73.75M H = MS 20 55.00 33.50 4.44 6.00 5.02 5.25 4.40 6.00 57.22 1.80 M 1.50 M D = 70.5.00 H MS 21 60.00 37.00 3.30 5.32 6.85 4.88 2.80 6.85 52.91 Nil 1.80 M D = 24.60M H D = 79.60 M H= MS 22 65.00 39.20 4.90 5.20 5.65 3.33 2.50 5.65 52.53 = 1.80 M 1.00 M D= 66.20 H = D = 25.40 M H = MS 23 70.00 50.40 8.10 9.50 5.55 3.27 2.90 9.50 82.84 2.00 M 1.00 D = 241.86M H D = 52.86 M H= MS 24 75.00 79.72 4.50 4.95 4.90 3.12 2.60 4.95 73.11 2.20 M 2.00 M D = 50.70 M H D = 200.20 MS 25 80.00 66.40 4.85 5.05 4.50 4.80 4.10 5.05 78.22 = 2.08 M H=1.50 M D = 27.05 M H D =192.05 M H= MS 26 85.00 44.10 4.10 5.80 6.00 5.10 3.90 6.00 63.20 = 1.50 M 1.70 M D = 97.88 M H= MS 27 90.00 54.35 4.90 5.52 3.90 3.65 2.85 5.52 61.24 Nil 1.60 M MS 28 94.00 60.10 4.00 4.75 4.50 3.12 2.77 4.75 58.65 Nil Nil MS 29 99.00 45.40 2.92 4.30 4.46 4.05 3.10 4.46 48.40 Nil Nil MS 30 0.00 70.20 4.10 4.70 7.33 5.20 4.10 7.33 82.43 Nil Nil

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Table 2.10 : Flow area Details of Longai River system-Contd Distance from Embankment Details Vertical depth (m) Maximum flow area Name of bangladesh Maximum top Name of station depth(m) (Approx ) in station border( Latu width (T) in (M) 1/6.T 2/6.T 3/6.T 4/6.T 1/6.T Sq.m R Bank L Bank Bridge) MS 34 12.00 57.50 4.80 5.95 8.95 6.83 5.50 8.95 92.81 Nil Nil MS 35 16.00 63.70 4.30 5.20 6.30 5.90 4.98 6.30 84.06 Nil Nil MS 36 18.00 58.80 4.90 5.80 7.40 6.20 5.40 7.40 89.27 Nil Nil MS 37 20.00 65.30 3.90 5.80 8.40 6.85 5.75 8.40 94.61 Nil Nil MS 38 22.00 57.20 2.95 4.52 4.85 3.80 3.10 4.85 55.18 Nil Nil

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Flood Damage Mitigation: Report Fig 2.20(a) : Section Details of Longai River system

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Flood Damage Mitigation: Report Fig 2.20(b) Section Details of Longai River system-contd

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Flood Damage Mitigation: Report Fig 2.20(c) Section Details of Longai River system-contd

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Name of the river - Barak Left bank Right bank From to Approx length from to Approx length Dilcush village Rajnagar 84 Km Barenga Masughat 42 Km Ujan Gram Katigorah 40 km

Name of the river - Rukni Left bank Right bank From To Approx length from to Approx length Baga Nadir gram 30.50 Km Gagla ghat Roy para 24 Km

Name of the river - Sonai Left bank Right bank From To Approx length from to Approx length Borali basti Jarul gram toal 33.50 Km Amraghat Dungir par 38.00 Km

Name of the river - Badri Left bank Right bank From To Approx length from to Approx length Mach para Badri basti 2.00 Km Old lakhipur Machpara 1.50 Km road

Name of the river - Madhura Left bank Right bank From To Approx length from to Approx length Rongpur Istampur 14.00 Km Dudhpatil Pachmile 8.00 Km

Name of the river - Gagra Left bank Right bank From To Approx length from to Approx length Rothur gram 6 A.P camp 19.50 Km Suktara Srikona 2.00 Km

Name of the river -jatinga Left bank Right bank From To Approx length from to Approx length Badripar dolu 3.00 Km - - -

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Name of the river –katakhal

Left bank Right bank From To Approx length from to Approx length kaligange Rupacherra 71.00 Km kaligange Rupacherra 71.00 Km Bagan

Name of the river –Longai Left bank Right bank From To Approx length from to Approx length Gandhri Baitar Ghat 57.00 Km Nilambazer buringa 49.00 Km

Table- 2.12 Details of existing major sluice gates in Barak Valley

Sl Sluice Gate River/ Channel Outfall no. 1. Surface Sluice(Five Openings) Suktara Channel Ghagra

2. Larsing Sluice(Single Opening) Larsing Channel Madhura

3. Paku Sluice(Double Opening) Amjur River Sonai

4. Boile Badri(old)(Double shutter) Bolie Badri Jatinga

5. Boile Badri(new)(Double shutter) Bolie Badri Jatinga

6. Punir Mukh Sluice(Duoble Shutter) Rukni River Rukni

7. Rangirkhari Sluice (Single Shutter) Rangirkahri Channel Ghagra

8. Purkhai Sluice(Single Shutter) Purkhai Borak

9 PirNagar Sluice gate (multiple Shutter) Baleshwar Surma

10 Sluice gate (Village Muraure) Churia Jhumjhumi - Channel 11 Pola Sluice(Shutters:4 nos) Pola Chnnel Barak

12 Hatia Diversion Sluice(Single Shuttter) Dhaleshwar Dhaleshwar

13 Lalatol Sluice (Shutters:2 nos) Katakhal River Katakhal

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3.0 Rainfall Analysis:

The Barak Valley is situated in the southern part of Assam and consists of Cachar, Hailakandi and Karimganj districts. The entire area of this valley lies within the hydro-meteorological Sub-Zone 2(C) of India. Reliable rainfall frequency analysis for the sites can be carried out if the available data are of longer periods as compared to the desired return periods. In order to gather rainfall affecting information from those of the ungaged areas roughly 14 numbers of (10 latitude X 10 longitude) grid points are selected to cover the entire study area. The large scale atmospheric variables affecting rainfall and seasonality of rainfall data for each of the grid points are extracted from NCEP Operational Plotting Page ( www.esrl.noaa.gov/psd/data/hisdata/) and GPCC Precipitation Data Set (www.esrl.noaa.gov) which are used along with the location parameters ( latitude and longitude) as attributes for the regionalization of the Sub-Zone into two homogeneous regions by Fuzzy c-means clustering. The use of large scale atmospheric variables as attributes can form reliable regions than the use of site data alone because these variables give information from the ungauged areas. The two delineated regions are tested for discordancy and regional homogeneity using the site data available in the grid points. L-moment based index-rainfall approach ( Hosking and Wallis 1990, 1993, 1997) is used for the rainfall frequency analysis of this Valley. In case of the gauged sites a regional rainfall frequency relationship for the estimation of rainfall of various return periods was derived using the selected distributions whereas for those of the ungauged sites a regional mean rainfall relationship with latitude and longitude of the sites was developed using multiple linear regression. The objectives of this study is to conduct regional extreme rainfall frequency analysis for Barak Valley of India using L-moments approach.

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3.1 Study Area and Data Collection

This study area lies within 220 N to 270 N and 900E to 950 E which covers the states of Meghalaya, Manipur, Nagaland, Mizoram, Tripura, North Cachar Hills and Barak Valley of Assam. The entire study area can be roughly covered by 14 numbers of 10 Latitude x 10 Longitude grid points. The maximum annual daily rainfall data from 1990 to 2010 for 13 nos. of stations in this valley are collected from Regional Meteorological Centre, Gauwahati. The 14 grid points with the stations in the grid are in Table 14. The gridded (10 x 10) large scale atmospheric variables affecting rainfall in the grids of the study area are extracted from NCEP ( National Centre for Environmental Prediction) Operational Plotting Page ( www.esrl.noaa.gov/psd/data/hisdata/) and gridded (10 latitude x 10 longitude) precipitation data from Global Precipitation Climatory Centre (www.esrl.noaa.gov).

Figure-3.1: Grid Points Covering the Study Area

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Grid Latitude Longitude Stations in the Latitude Longitude Length of Poin Grid Record ts

Table- 3.1: Rainfall gauging station in the selected Grids

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3.2 L-moments Approach:

L-moments are linear combinations of probability weighted moments (PWM). The probability weighted moments are calculated from the ranked observations X1 > X2 > X3 ……………> Xn. Greenwood et al (1979) summarizes the theory of probability weighted moments and defined them as

-1 j 1 j 2 ..(j r) br = N 푁 N 1 N 2 N 3 ..(N r) = +1 − − …………………… − 푗 푗 푟 푥 − − − ……… − The first four L-moments are

ʎ1 = β0ʎ2 = 2 β1 - β0ʎ3 = 6 β2 - 6β1 + β0ʎ4 = 20 β3 - 30β2 +12 β1- β0

where ʎ1 is the L-mean which measures the central tendency, ʎ2 is the L- standard deviation which measures the dispersion. Again,(Hosking, 1990) defined the dimensionless L-moment ratios

2 3 = L- coefficient of variance, L-cv = , 3 = L- skewness = , 4 = L- ʎ1 ʎ2 kurtosis휏 = 4 ʎ 휏 ʎ 휏 ʎ2 ʎ

3.3 Discordancy measure

Hosking & Wallis (1993) defined discordancy measure of sites to detect the discordance sites among other sites as D = 1 (u T A-1(u i 3 i – ū ) i – ū ) where, T ui = ( , 3, 4) is a vector containing , 3, 4 values of site i, the superscript

T denotes휏 휏 transpose휏 of a matrix or vector,휏 휏 휏

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-1 the covariance푁 matrix A of ui The elements of A are given by the relation,

A = 1 u T ,where N is the number of sites in the =1( i – ū )(ui – ū ) 푁 region. 푁 푗

The discordancy (Di) of the 13 sites are determined and the station

Lengpui has its Di value greater than the critical value of 2.869 for 13 stations. The valley has to be sub-divided into regions to see whether the

Di value of this site can be adjusted below the critical value by combining with some other sites and to form hydrologically similar homogeneous regions using Fuzzy c-means clustering.

3.4Fuzzy c-means clustering -

In this study Fuzzy c-means clustering is carried out in MATLAB using large scale atmospheric variables affecting rainfall, location parameters and seasonality of rainfall as attributes. Two regions are formed by assigning the membership of each grid points in the clusters equal or greater than to a threshold; T = max { 1 , 1 [max (µ )]}, where c = i c 2 ij th th no. of clusters and µij = maximum membership of the i grid point in the j cluster. These two regions consist of grid point 1 to 5 in region I and 6 to

14 grid points in region II. The Di values for the sites in the two regions are less than their respective critical values i.e.1.333 for Region I and 2.329 for Region II which indicates that there are no discordance sites.

Annual maximum rainfall intensity for the rain gauging stations in the valley for last 21 years from 1990 to 2010 is collected from RMC Guwahati. The annual maximum rainfall in recorded for various station are used to estimate 10,20,30,40,50,75 and 100 year return period rainfall intensity for the gauging stations. Estimation of extreme rainfall intensity for this valley is obtained from the regional extreme rainfall frequency analysis of the

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Flood Damage Mitigation: Report sub-zone. Here, L-moments based regional frequency analysis approach is used. The discordancy(Di) measure for screening out the data of the unusual sites was conducted. Fuzzy c-means clustering analysis with location parameters, seasonality of rainfall and large scale atmospheric variables affecting rainfall in the study area was used as attributes for regionalization of the Sub-Zone into homogeneous regions. Heterogeneity measure has been conducted by carrying out 500 simulations using a 4- parameter Kappa distribution. Five extreme value distributions Generalized Pareto (GPD), Generalized Logistic (GLO), Generalized Extreme Value (GEV), Pearson Type III and Log Normal (LN3) were used to select the best fit distribution for the regions. Based on ZDIST statistics and L-moment ratio diagrams GLO for region I and GPD for region II were selected as the best fit distributions. Regional rainfall formula for the estimation of rainfall for various return periods was derived for the gauged sites using the selected distributions and growth factors for the regions were derived. For the ungauged sites a regional mean relationship with latitude and longitude of the sites were developed using multiple linear regression. Brief methodology applied in analyzing the extreme rainfall events is summarized below:

3.5 Brief Methodology:

L-moment approach analysis (Hosking & Wallis, 1990) consists of the following steps-

(a) Screening of data using a discordancy measure.

(b) Formation of homogeneous regions using clustering method and refinement by conducting homogeneity test.

(c) Choice of distribution using Goodness of fit test – ZDIST statistics and L-moment ratio diagram.

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Flood Damage Mitigation: Report (d) Establishment of rainfall frequency relationship using index- flood/rainfall method and Development of regional growth curves.

The discordancy (Di) measure of the 13 sites are conducted and one of the sites has its Di value greater than the critical value of 2.869 for 13 sites

(Hosking & Wallis). To adjust this Di value below the critical value and to include this site in the analysis, the study area has been clustered into two regions- region I comprising the grid points (1, 2, 3, 4 & 5) and region II comprising the grid points (6, 7, 8, 9, 10, 11, 12, 13 & 14) respectively using Fuzzy c-means clustering in MATLAB with large scale atmospheric variables affecting rainfall, location parameters and seasonality of rainfall as attributes and refinement by conducting homogeneity test. The heterogeneity measure has been conducted by carrying out 500 simulations using a 4-parameter Kappa distribution in a computer programme written in JAVA. From the result of Goodness of fit test using ZDIST statistics and L-moment ratio diagram, GLO for region I and GPD for region II have been selected as the best fit distribution. The parameters of the selected distributions are estimated using L-moments and regional growth factors are derived by index-flood procedure(Dalrymple, 1960) with the development of regional rainfall formula for the two regions as –

Region I

(1 F ) X = [0.43096 + 0.50370 { }-0.26895] . X (3.1) T F −

Region II

0.59644 XT = 1.69161 – 1.10411 (1- F ) . X (3.2)

1 Where, X = at site mean rainfall, F = (1 - ) and T = return period. T

T-year rainfall intensity for Barak Valley of Assam is carried out using (3.2) as this valley lies within region II.

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Flood Damage Mitigation: Report Table-3.2 : Estimated T-year rainfall intensity for Barak Valley

Station Year 10 20 30 40 50 75 100 Silchar 170.17 181.05 185.63 188.26 190.01 192.66 194.19 Dholai 174.72 185.89 190.59 193.30 195.09 197.81 199.38 Karimganj 244.75 260.39 266.98 270.77 273.28 277.09 279.29 Gharmura 176.77 188.07 192.83 195.57 197.38 200.14 201.73

3.6 Development of Regional mean rainfall relationship -

The regional mean rainfall relationship is established by relating rainfall with latitude and longitude of the sites using matrix method of linear regression. The rainfall means for the observed data for the two stations in region II i.e. Cherrapunji and Mawsynram have extremely high values than the rest of all stations. So region II have been divided into two regions based on mean values and geographical locations of the grids as region II (a) comprising of grid points ( 6,7,8,12,13 and 14) and region II (b) comprising of grid points ( 9,10 and 11). Three linear equations have been developed as in (3.3), (3.4) and (3.5) for the estimation of mean rainfall for the sites in these regions.

Region I X = 2630.3 + 3.7( Lat.) – 28.1 ( Lon.) (3.3)

Region II (a) X = 2630.3 + 3.7( Lat.) – 28.1 ( Lon.) (3.4)

Region II (b) X = 2630.3 + 3.7( Lat.) – 28.1 ( Lon.) (3.5)

where (Lat.) is latitude and (Lon.) is the longitude for the site.

Regional mean rainfall for Barak Valley of Assam is estimated using (3.4) as this valley lies within region II(a).

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Table-3.3: Estimation of mean rainfall using regional mean relationship

Station Observed Estimated ( ) χ2 = mean (Q) Lat Lon mean( E) ퟐ ∑ 푸−푬 1.Silchar 128.58 24.81 92.80 144.84 1.8250푬 2. Dholai 132.02 24.58 92.85 133.44 0.0152 3. Karimganj 184.93 24.86 92.35 175.07 0.5556 4. Gharmura 133.57 24.36 92.53 145.79 1.0246

Chi- Square χ2 3.4204

The Chi-Square values for the estimated mean and observed means for region II (a) is 3.4204 against the critical values of 7.815 at 95% significance level with 3 degrees of freedom. This shows that there is no significance difference between the estimated mean and observed mean.

4.0 Watershed Modeling:

4.1 Geographic Information System (GIS)

Geographic information system is an advanced software system engineered to enable creation, use, and management and sharing of geographic information viz.: geographic data set and data models, maps and globes, geoprocessing models and scripts, GIS methods and workflows and metadata. GIS combines a powerful visualization environment with a strong analytic and modeling framework that is rooted in the science of geography. GIS software supports several views for tackling with the geographic information categorized as the geodatabase view, the geovisualization view and geoprocessing view. In geodatabase view, GIS

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Flood Damage Mitigation: Report acts as a spatial database that connects datasets representing geographic information in terms of features, rasters, attributes, terrains, networks, etc. In geovisualization view, GIS acts as an advanced maps and other views that show features and feature relationships on the earth’s surface which enable storing, querying, analyzing, and displaying of geospatial data. Lastly, in geoprocessing view it acts as information transformation tools that can extract new data set from existing information. These geoprocessing functions take information from existing datasets, apply analytic functions, and write results into new derived datasets. Geoprocessing also involves the ability to program and to automate a sequence of operation on geographic data to create new information. The ability of GIS to handle and process geospatial data in which the characteristics variables varies spatially distinguishes GIS from other information system. ArcGIS Desktop is a professional GIS application that comprises of three main software products: ArcView, ArcEditor, and ArcInfo which provides a scalable framework for implementing GIS techniques in prominent field like hydrology, environmental sciences, etc.

Applying GIS techniques DEM models for the entire Earth surface have been generated by different agencies that are available free of cost. The United States Geological Survey (USGS) is the primary distributor of The Shuttle Radar Topography Mission (SRTM), developed jointly by the National Aeronautics and Space Administration (NASA) and the National Geospatial Intelligence Agency (NGA), providing elevation datasets. The SRTM is projected into a geographic coordinate system (GCS) with the WGS84 horizontal datum and the EGM96 vertical datum (USGS, 2006). The

Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is an advanced multispectral imager that was launched on board NASA’s Terra spacecraft in December, 1999. The ASTER Digital Elevation Model (DEM) product is generated using bands 3N (nadir-viewing) and 3B (backward-viewing) of an ASTER Level-1A image acquired by the Visible Near Infrared (VNIR) sensor. Apart from the DEM developed by discretizing

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Flood Damage Mitigation: Report the top maps these DEMs though may have some imperfections can be used as an input to quantify the characteristics of the land surface after rectification

4.2 Geomorphologic parameter estimation using GIS aided techniques

Estimation of geomorphologic parameters for a watershed can be achieved using different tools like hydrology, 3D analysis, Statistics, etc. in ArcGIS . These tools can be applied individually or used in sequence to create stream network to delineate watersheds. The process of estimation of geomorphologic characteristics of a watershed using GIS techniques involves the following sequential stepsas shown in the chart given in the next page:

4.3 Development of Digital Elevation Model (DEM) for the watersheds:

Digital Elevation Model for the important watershed in the study area are developed using GIS technique by applying ArcGIS software. Generation of DEM using topographic map can be accomplished by following the steps and applying different GIS tools as shown in the above chart. Survey of India (SOI) provides topographic maps of different scales like 1:25,000, 1:50,000, etc. Topographic maps for the study area were collected from the office of Survey of India, Shillong. The maps were processed and brought to GIS environment in .tiff format. Using GIS software ArcGIS, coordinate system are defined for the topographic maps using suitable projected/ geographic coordinate system available in GIS software. The georeferenced map is used as input in GIS platform and contour digitization is done using Editing tool. The completed vector data of digitized contour is used with 3D analysis tool to generate Triangulated Irregular Network (TIN). Further using generated TIN as input in 3D analysis tool, DEM for the watersheds are generated. In the present study

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Flood Damage Mitigation: Report DEM for Watersheds of Chiri, Jiri, Ghagar, Madhura, Jhatinga etc. are developed and given in the figures 4.2 to 4.6.

Figure-4.1: Flow chart for GIS application.

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Figure-4.2: Digital Elevation Model of Jiri sub basin

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Figure-4.3: Digital Elevation Model of Chiri sub basin

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Figure-4.4: Digital Elevation Model of Madhura sub basin

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Figure-4.5: Digital Elevation Model of Ghagra sub basin

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Figure-4.6: Digital Elevation Model of Jatinga sub basin

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Flood Damage Mitigation: Report 4.4Development Stream Network for the watersheds

For watersheds in the study area the corresponding DEMs are used to develop the stream network for these watersheds. The generated DEM are analyzed using, Calculate statistic GIS tooltaking the DEM as an input. The spatial analysis tool is used to develop depressionless DEM for the watersheds. Using the rectified DEM a raster of flow directions from each cell to its steepest downslope neighbor cell is created. Flow direction is generated using DEM as an input to Hydrology tool. The output of the flow direction tool is used to generate flow accumulation raster which is determined by accumulating the weight for all the cells that will flow into each cell. The generation of flow accumulation raster is achieved by using the generated flow direction raster as an input to Hydrology tool “flow accumulation”. A threshold value that gives the minimum number of upslope cells contributing to a downstream cell is required. The stream network raster for the watershedsare generated using Map Algebra/ Conditional tool. The generated stream networksare ordered using Strahler stream ordering tool in the ArcGIS.. It adopts Strahler’ Stream ordering law (Strahler, 1952) for ordering the stream network. In the Strahler ordering method, all streams with no tributaries are assigned an order of one and are referred to as first order. When two first-order streams intersect, the downslope stream is assigned an order of two. When two second-order streams intersect, the downslope stream is assigned an order of three, and so on. When two streams of the same order intersect, the order will increase. Strahler order method is the most common method used for ordering stream network. On the basis of the ordered stream network and flow direction map watershed area draining through different streams are delineated by using hydrology tool.

4.5 Generation of Slope map for watersheds using Topographic Map, SRTM/ASTER DEM.

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Flood Damage Mitigation: Report The slope map of a watershed represents the degree of steepness (slope) of the watershed surface at different locations. The Slope map in slope percent for the watersheds is developed using rectified DEM in 3D analysis tool. Detailed description of the sub basins in the study area, drainage networks and slope map for the sub basins are presented in the tables and figures listed below.

Figure-4.7: Drainage network in Jiri sub catchment

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Figure-4.8: Drainage network in Chiri sub catchment

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Figure-4.9: Drainage network in Madhura sub catchment

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Figure-4.10: Drainage network in Ghagra sub catchment

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Figure-4.11: Drainage network in Jatinga sub catchment

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Figure-4.12: Flow direction in Jatinga sub catchment

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Figure-4.13: Drainage network in Katakhal sub catchment

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Figure-4.14: Drainage network in Sonai sub catchment

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Figure-4.15: Slope map for Chiri sub catchment

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Figure-4.16: Slope map for Jiri sub catchment

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Figure-4.17: Slope map for Ghagra sub catchment

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Figure-4.18: Slope map for Madhura sub catchment

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Figure-4.19: Slope map for Jatinga sub catchment

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Figure-4.20: Slope map for Katakhal sub catchment

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Figure-4.21: Slope map for Sonai sub catchment

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Table-4.1: Watershed and Drainage Characteristics of Sub basins in the Study Area

Watersheds Drainage Stream Order Watershed Average Main stream Watershed Characteristics Area km2 Slope %  lengthkm  perimeter   1 2 3 4 5 6 km 

Total Count 781 177 42 10 3 1 349.43 0.28 52.61 170.85 Madhura Average stream 0.422 0.94 2.072 4.769 12.88 14.59 length (km) Total Count 506 131 33 7 2 1 409.39 0.09 48.93 157.84 Ghagra Average stream 0.659 1.04 2.487 5.907 9.803 19.784 length (km) Total Count 1083 277 56 9 3 1 1052.85 0.22 49.85 152.63 Jiri Average stream 0.635 1.37 2.429 11.69 14.86 48.09 length (km) Total Count 569 124 26 8 2 1 438.66 0.26 104.48 275.0 Chiri Average stream 0.59 1.46 3.39 4.36 19.80 11.62 length (km) Total Count 1183 282 68 19 4 1 1504.6801 10.64% 129.88 401.00 Katakhal Average stream 0.65 1.45 2.12 10.8 13.62 57.43 length (km) Total Count 417 100 25 2 1

371.86 35.085% 55.39 156.00 Jatinga Average stream 0.55 1.03 2.10 4.32 22.93 length (km) Total Count 614 169 37 08 02 01 Sonai 488.249 7.798% 95.212 203 Average stream 0.60 1.36 3.21 4.11 11.05 15.976 length (km)

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5.0 Hydrological Modeling: Development of Unit Hydrographs

Hydrologic responses of a watershed are influenced by geomorphologic characteristics of the watershed. Characterization and quantification of such characteristics is useful and essential in the process of evaluating the hydrologic response of a watershed. These characteristics relate to the physical characteristics of the drainage basin and drainage network; physical characteristics of the drainage basin include drainage area, basin shape, ground slope, and centroid (i.e. centre of gravity of the basin). Channel characteristics include channel order, channel length, channel slope, channel profile, and drainage density. Handling and modeling of such spatially varying parameters have become more efficient and accurate with the emergence of advance computing techniques, Geographic Information System (GIS). For deriving UH using GIUH models different watershed characteristics such as stream length, watershed area, slope, etc are essential. Using topographic maps/SRTM/ASTER data and remote sensing data in GIS software like ArcGIS, ERDAS imagine, ILWISS, etc Digital Elevation Model (DEM) can be developed and analyzed. With DEM as an input to quantify the watershed characteristics slope map, stream map, etc may be obtained. Watershed characteristics for the sub basins in the study areathat were estimated by using GIS supported techniquesis given in table-4.1. DEM, Stream networks and the slope maps for the watersheds in the study area are also presented in the earlier sections. Using DEM flow direction and flow accumulation maps for the watersheds are developed. With the drainage network map as input and using Strahler’s stream ordering law the drainage network for the watersheds are ordered applying GIS stream ordering tool. On the basis of the ordered drainage network, areas drained and stream lengths for different stream orders are obtained. Horton’s geomorphologic parameters (Horton, 1945) RA , RB and RL for the watershed are estimated graphically by plotting average areas drained, stream numbers and average stream length respectively against the stream orders. Absolute slope value for the best fit line is taken to compute the ratios. Graphical representations showing best fit line is used for computing RA , RB and RL for the watersheds.

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The best fit lines for Madhura and Ghagra watersheds are shown in Figures. Estimated geomorphologic parameters for all watersheds are given in the Table- 4.1. Estimated watersheds mean slope and main stream length values are used in equation (5.1) to obtain velocity factor for the watersheds respectively. The velocity parameter estimated for Madhura and Ghagra watersheds are listed in the Table-5.2. The listed parameters are used to develop triangular based 1hr UHs for the watersheds applying GIUH techniques.

The GIUH model given by equations (5.1), (5.2) and (5.3) are used to estimate peak discharge, time to peak and time base of the IUH for the watersheds in the study area.

.0 23 .0 385 V  .0 8562L S (5.1)

.0 43 qp  .1 31RL V L  (5.2)

.0 55  .0 38 t p  .0 44L V RB RA  RL  (5.3) tb  2 q p (5.4)

1 Here, q p  peak flow in units of inverse hours h ; t p  time to peak in hours h 

; V  dynamic parameter velocity m/ s ; L  length of the highest order stream in the watershed km ; and RL ,RB and RA = Horton’s length ratio, bifurcation ratio and area ratio respectively. To develop IUH for the watersheds dynamic parameter velocity estimated for the watersheds and listed in Tables are used in equations (5.2) and (5.3) obtaining q p ,t p and tb values for the watersheds.To develop UH for the watersheds the subbasins are segmented into a number subwatersheds and IUH for these subwatersheds are computed applying GIUH technique. The sub water IUHs are lagged to develop 1-hr UH for the sub watersheds. The UHs routed to the main watershed outlet using kinematic wave technique and superimposed obtaining IUH for the main watershed.Detailed description of unit hydrograph computation for two watersheds, Madhura and Ghagra watersheds are listed.IUH ordinates for the watersheds at an interval of

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1.0 h are computed and lagged applying S-Curve technique to derive 1hr UH for the watersheds. 1-hr UH estimated for the watersheds using GIUH technique are shown in the figures and tables presented in the next pages.

Figure-5.1: 1st order watersheds for Madhura

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Figure-5.2: 2nd Order sub-watersheds for Madhura.

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Figure-5.3: 2nd Order sub-watersheds for Madhura.

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Figure-5.4: 3rd Order sub-watersheds for Madhura

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Figure-5.5: 4th Order sub-watersheds for Madhura.

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Figure-5.6: 5th Order sub-watersheds for Madhura.

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Figure-5.7: Madhura watershed (6th Order).

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Figure-5.8: 1st Order sub-watersheds for Ghagra.

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Figure-5.9: 2nd order sub-watersheds for Ghagra.

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Figure-5.10: 3rd Order sub-watersheds for Ghagra.

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Figure-5.11: 4th Order sub-watersheds for Ghagra.

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Figure-5.12: 5th order sub-watersheds for Ghagra.

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Figure-5.13: Ghagra watershed (6th order).

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The Subwatersheds selected for Madhura for development of IUH are indicated in the figure given below:

Figure-5.14: Selected sub-watersheds for Madhura.

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Subwatersheds in Ghagra selected for developing IUH are as given in the figure given below:

Figure-5.15: Selected sub-watersheds for Ghagra.

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Applying conversion tool the raster file of ordered stream network, area drained are converted into vector file and extracted in Microsoft Office Excel worksheet. Using the extracted data sub-watersheds average stream length, stream numbers, average area drained by different orders of stream are obtained. Horton’s geomorphologic parameters RA ,RB and RL for the sub- watersheds are estimated graphically by plotting the estimated average areas drained, stream numbers and average stream length respectively against the stream orders. Absolute slope values for the best fit line are taken to compute the ratios. Graphical representations showing best fit lines used for computing

RA ,RB and RL for respective sub-watersheds are shown in Figures-516 through 5.27.

7 Area Ratio Bifurcation Ratio 6 Length Ratio

5 y = 1.607x - 3.073 R² = 0.995

y = -1.486x + 7.494 4 R² = 0.999

3

Ln avg.LnA/ Lnavg. L/Ln N 2 y = 0.940x - 1.933 R² = 0.972

1

0 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 Stream Order

1 Figure 516: Estimation of ratios RA ,RB and RL for MSW5 .

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6 Area Ratio Bifurcation Area

5 y = -1.326x + 6.319 Length Ratio R² = 0.986

4 y = 1.409x - 2.711 R² = 0.999

3

2

Ln avg. A/ Ln Ln avg. L/ N avg. Ln y = 0.847x - 1.743 1 R² = 0.994

0 0 1 2 3 4 5 6 Stream Order

2 Figure 5.17: Estimation of ratios RA ,RB and RL for MSW5 .

6 Area Ratio y = -1.269x + 6.232 R² = 0.997 Bifurcation Area 5 Length Ratio y = 1.418x - 2.724 R² = 0.997

4

3

y = 0.618x - 1.331 2 R² = 0.897 Ln avg. A/ Ln avg. L/ Ln N Ln L/ avg.Ln A/ avg.Ln

1

0 0 1 2 3 4 5 6 Stream Order

3 Figure 5.18: Estimation of ratios RA ,RB and RL for MSW5 .

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2.5 Area Ratio y = 0.624x - 1.374 Bifurcation Ratio R² = 0.832 2 Length Ratio

1.5

1 y = -1.098x + 3.391 R² = 0.977

0.5 y = 1.365x - 2.575 R² = 0.996

0 0.5 1 1.5 2 2.5 3 3.5 Ln avg. A/ Ln avg. L/ Ln N Ln L/ avg.Ln A/ avg.Ln -0.5

-1

-1.5 Stream Order

1 Figure 5.19: Estimation of ratios RA ,RB and RL for MSW3 .

6 Area Ratio Bifurcation Ratio 5 Length Ratio

y = 1.476x - 2.263 4 R² = 0.998

3

2

Ln avg. A/ Ln avg. L/ Ln A/ avg.L/ N Ln avg.Ln Ln y = -1.364x + 6.715 R² = 0.997

1 y = 0.747x - 1.307 R² = 0.996

0 0 1 2 3 4 5 6 Stream Order

1 Figure 5.20: Estimation of ratios RA ,RB and RL forGSW5 .

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5 Area Ratio

4.5 Birfurcation ratio

Length ratio 4 y = 1.310x - 1.860 R² = 0.993 3.5 y = -1.192x + 5.694 R² = 0.986 3

2.5

2

1.5 y = 0.624x - 1.011 Ln avg. A/ Ln avg. L/ Ln N Ln L/ avg.Ln A/ avg.Ln R² = 0.983 1

0.5

0 0 1 2 3 4 5 6 Stream Order

2 Figure 5.21: Estimation of ratios RA ,RB and RL forGSW5 .

5 Area ratio Bifurcation ratio 4 Length ratio y = -1.471x + 6.031 R² = 0.993 y = 1.585x - 2.460 3 R² = 0.970

2 y = 0.996x - 1.741 R² = 0.844 1

Ln avg. A/ Ln avg. L/ Ln N Ln L/ avg.Ln A/ avg.Ln 0 0 1 2 3 4 5

-1

-2 Stream Order

1 Figure 5.22: Estimation of ratios RA ,RB and RL forGSW4 .

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3.5 Area ratio Bifurcation ratio 3 Length ratio 2.5 y = 1.250x - 1.789 R² = 0.989 2 y = -1.090x + 4.191 R² = 0.983

1.5

1

0.5 y = 0.414x - 0.888 R² = 0.821 Ln avg. A/ Ln avg. L/ Ln N Ln L/ avg.Ln A/ avg.Ln 0 0 1 2 3 4 5 -0.5

-1 Stream Order

2 Figure 5.23: Estimation of ratios RA ,RB and RL forGSW4 .

3.5 y = 1.307x - 2.199 Area Ratio R² = 0.974 3 Bifurcation Ratio

2.5 Length Ratio

2

1.5 y = -1.262x + 4.478 R² = 1 1

0.5 y = 0.650x - 1.281 R² = 0.998 0 Ln avg. A/ Ln avg. L/ Ln N Ln L/ avg.Ln A/ avg.Ln 0 0.5 1 1.5 2 2.5 3 3.5 -0.5

-1

-1.5 Stream Order

1 Figure 5.24: Estimation of ratios RA ,RB and RL forGSW3 .

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4.5 Area ratio Bifurcation ratio 4 y = 1.800x - 3.176 Length ratio R² = 0.966 3.5

3

2.5

2

1.5

1 Ln avg. A/ Ln avg. L/ Ln N Ln L/ avg.Ln A/ avg.Ln

0.5 y = -1.589x + 6.423 0 R² = 0.994 1 1.5 2 2.5 3 3.5 4 4.5 -0.5

Stream Order

2 Figure 5.25: Estimation of ratios RA ,RB and RL forGSW3 .

2.5 Area ratio Bifurcation ratio Length ratio

2

1.5 y = 0.865x - 1.242 R² = 0.845

1

0.5 y = 0.521x - 1.032 R² = 0.843 Ln avg. A/ Ln avg. L/ Ln N Ln L/ avg.Ln A/ avg.Ln y = -1.148x + 3.558 0 R² = 0.972 0.5 1 1.5 2 2.5 3 3.5

-0.5 Stream Order

3 Figure 5.26: Estimation of ratios RA ,RB and RL forGSW3 .

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2.5 Area ratio Bifurcation ratio 2 Length ratio

1.5 y = 1.310x - 2.498 R² = 0.997 y = 0.524x - 1.141 1 R² = 0.847

0.5

y = -1.048x + 3.225 0 R² = 0.983 0.5 1 1.5 2 2.5 3 3.5 Ln avg. A/ Ln avg. L/ Ln N Ln L/ avg.Ln A/ avg.Ln -0.5

-1

-1.5 Stream Order

4 Figure 5.27: Estimation of ratios RA ,RB and RL forGSW3 .

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Table 5.1: Geomorphologic characteristics of sub watersheds of Ghagra and Madhura

Sub- Area Length Bifur Main Highest Area Average Velocity watersheds Ratio Ratio cation stream Order slope V  Ratio length Stream A  m/ s  R  R  Length 2 S  A L km 

RB  L  m/ m 

km  L  km  1 4.98 2.56 4.15 38.02 21.39 170.07 0.39 6.74 MSW5 2 4.09 2.33 3.77 24.83 13.01 73.14 0.27 5.33 MSW5 3 4.13 1.86 3.56 17.31 4.23 72.78 0.09 3.26 MSW5 1 3.92 1.87 2.99 7.18 1.94 4.80 0.08 2.54 MSW3 1 4.38 2.11 3.91 26.15 11.57 163.74 0.09 3.51 GSW5 2 3.71 1.87 3.29 28.58 8.04 92.17 0.11 3.88 GSW5 1 4.88 2.71 4.35 23.50 15.88 68.08 0.1 3.57 GSW4 2 3.49 1.5 3.00 6.89 2.00 21.26 0.08 2.47 GSW4 1 3.69 1.62 3.11 4.67 2.11 6.33 0.02 1.22 GSW3 2 3.19 1.56 3.00 3.65 0.80 1.94 0.07 1.97 GSW3 3 3.69 1.74 3.11 5.88 2.01 7.62 0.02 1.25 GSW3 4 3.58 1.81 3.21 3.68 1.01 4.56 0.11 2.42 GSW3

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Ta

Hydraulic ble L Watershed flow Slope V(m/s) Ra Rb Rl omega(km) - length (m) 5.2 GHAGRA 48930 0.098 4.19 19.784 3.90 3.64 2.022 : MADHURA 52609 0.28 6.39 14.589 4.305 3.826 2.125 Mo CHIRI 49881 0.23 5.85 11.645 3.815 3.504 1.906 rph JIRI 103240 0.29 7.56 48.09 4.56 4.21 2.44 olo KATAKHAL 129880 0.11 5.49 57.43 4.35 4.1 2.406 gic JATINGA 55390 0.35 7.04 22.93 4.01 4.9 3.089 al SONAI 95212 0.07 4.29 15.976 3.5 3.8 1.9251 par ameters for the subcatchments

3 Table 5.3: 1hr UH ordinates for MSW5 .

Time GIUH GIUH S-curve S-curve lagged by 1hr UH (Hours) ordinate lagged SUM/2 addition ordinate 10x0.1 hr ordinate

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0 0 0 0 0

0.1 66.60425 0 33.302125 0 33.30213 3.3302125

0.2 133.2085 66.60425 99.906375 33.302125 133.2085 13.32085

0.3 199.81275 133.2085 166.510625 133.2085 299.7191 29.971913

0.4 266.417 199.81275 233.114875 299.719125 532.834 53.2834

0.5 242.2 266.417 254.3085 532.834 787.1425 78.71425

0.6 217.98 242.2 230.09 787.1425 1017.233 101.72325

0.7 193.76 217.98 205.87 1017.2325 1223.103 122.31025

0.8 169.54 193.76 181.65 1223.1025 1404.753 140.47525

0.9 145.32 169.54 157.43 1404.7525 1562.183 156.21825

1 121.1 145.32 133.21 1562.1825 1695.393 0 169.53925 1.1 96.88 121.1 108.99 1695.3925 1804.383 33.302125 177.10804 1.2 72.66 96.88 84.77 1804.3825 1889.153 133.2085 175.5944 1.3 48.44 72.66 60.55 1889.1525 1949.703 299.719125 164.99834 1.4 24.22 48.44 36.33 1949.7025 1986.033 532.834 145.31985 1.5 0 24.22 12.11 1986.0325 1998.143 787.1425 121.1 1.6 0 0 1998.1425 1998.143 1017.2325 98.091

1.7 1998.1425 1998.143 1223.1025 77.504

1.8 1998.1425 1998.143 1404.7525 59.339

1.9 1998.1425 1998.143 1562.1825 43.596

2 1998.1425 1998.143 1695.3925 30.275

2.1 1998.1425 1998.143 1804.3825 19.376

2.2 1998.1425 1998.143 1889.1525 10.899

2.3 1998.1425 1998.143 1949.7025 4.844

2.4 1998.1425 1998.143 1986.0325 1.211

2.5 1998.1425 1998.143 1998.1425 0

2.6 1998.1425 1998.143 1998.1425

1 Table5.4: 1hr UH ordinates for GSW5 .

Time GIUH GIUH S-curve S-curve lagged by (Hours) ordinate lagged SUM/2 addition ordinate 10x0.1 hr 1hr UH ordinate

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0 0 0 0 0 0.1 24.969 0 12.4845 0 12.4845 1.24845 0.2 49.938 24.969 37.4535 12.4845 49.938 4.9938 0.3 74.907 49.938 62.4225 49.938 112.3605 11.23605 0.4 99.876 74.907 87.3915 112.3605 199.752 19.9752 0.5 124.845 99.876 112.3605 199.752 312.1125 31.21125 0.6 149.814 124.845 137.3295 312.1125 449.442 44.9442 0.7 174.783 149.814 162.2985 449.442 611.7405 61.17405 0.8 199.752 174.783 187.2675 611.7405 799.008 79.9008 0.9 224.721 199.752 212.2365 799.008 1011.245 101.1245 1 249.69 224.721 237.2055 1011.245 1248.45 0 124.845 1.1 240.067 249.69 244.8785 1248.45 1493.329 12.4845 148.0844 1.2 230.464 240.067 235.2655 1493.329 1728.594 49.938 167.8656 1.3 220.861 230.464 225.6625 1728.594 1954.257 112.3605 184.1896 1.4 211.258 220.861 216.0595 1954.257 2170.316 199.752 197.0564 1.5 201.655 211.258 206.4565 2170.316 2376.773 312.1125 206.466 1.6 192.052 201.655 196.8535 2376.773 2573.626 449.442 212.4184 1.7 182.449 192.052 187.2505 2573.626 2760.877 611.7405 214.9136 1.8 172.846 182.449 177.6475 2760.877 2938.524 799.008 213.9516 1.9 163.243 172.846 168.0445 2938.524 3106.569 1011.245 209.5324 2 153.64 163.243 158.4415 3106.569 3265.01 1248.45 201.656 2.1 144.037 153.64 148.8385 3265.01 3413.849 1493.329 192.052 2.2 134.434 144.037 139.2355 3413.849 3553.084 1728.594 182.449 2.3 124.831 134.434 129.6325 3553.084 3682.717 1954.257 172.846 2.4 115.228 124.831 120.0295 3682.717 3802.746 2170.316 163.243 2.5 105.625 115.228 110.4265 3802.746 3913.173 2376.773 153.64 2.6 96.022 105.625 100.8235 3913.173 4013.996 2573.626 144.037 2.7 86.419 96.022 91.2205 4013.996 4105.217 2760.877 134.434 2.8 76.816 86.419 81.6175 4105.217 4186.834 2938.524 124.831 2.9 67.213 76.816 72.0145 4186.834 4258.849 3106.569 115.228 3 57.61 67.213 62.4115 4258.849 4321.26 3265.01 105.625 3.1 48.007 57.61 52.8085 4321.26 4374.069 3413.849 96.022 3.2 38.404 48.007 43.2055 4374.069 4417.274 3553.084 86.419 3.3 28.801 38.404 33.6025 4417.274 4450.877 3682.717 76.816 3.4 19.198 28.801 23.9995 4450.877 4474.876 3802.746 67.213 3.5 9.595 19.198 14.3965 4474.876 4489.273 3913.173 57.61 3.6 0 9.595 4.7975 4489.273 4494.07 4013.996 48.0074 3.7 0 0 4494.07 4494.07 4105.217 38.88535 3.8 4494.07 4494.07 4186.834 30.7236 3.9 4494.07 4494.07 4258.849 23.52215 4 4494.07 4494.07 4321.26 17.281

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4.1 4494.07 4494.07 4374.069 12.00015 4.2 4494.07 4494.07 4417.274 7.6796 4.3 4494.07 4494.07 4450.877 4.31935 4.4 4494.07 4494.07 4474.876 1.9194 4.5 4494.07 4494.07 4489.273 0.47975 4.6 4494.07 4494.07 4494.07 0

400 1hr UH MSW15 (GIUH) 350 1hr UH MSW15 (NRCS)

300

250

200

150 Discharge(Cumec)

100

50

0 0 1 2 3 4 5

Time (Hours)

1 Figure 5.28: 1hr UH for Madhura sub-watershed MSW5 .

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200.00 1hr UH MSW25 (GIUH) 180.00 1hr UH MSW25 (NRCS) 160.00

140.00

120.00

100.00

80.00 Discharge(Cumec) 60.00

40.00

20.00

0.00 0 0.5 1 1.5 2 2.5 3 3.5 4

Time (Hours)

2 Figure 5.29: 1hr UH for Madhura sub-watershed MSW5 .

200 1hr UH MSW35 (GIUH) 180 1hr UH MSW35 (NRCS) 160

140

120

100

80 Discharge(Cumec) 60

40

20

0 0 0.5 1 1.5 2 2.5 3

Time (Hours)

3 Figure 5.30: 1hr UH for Madhura sub-watershed MSW5 .

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20 1hr UH MSW13 (GIUH) 18 1hr UH MSW13 (NRCS) 16

14

12

10

8 Discharge(Cumec) 6

4

2

0 0 0.5 1 1.5 2 2.5

Time (Hours)

1 Figure 5.31: 1hr UH for Madhura sub-watershed MSW3 .

300 1hr UH GSW15 (GIUH)

1hr UH GSW15 (NRCS) 250

200

150

Discharge(Cumec) 100

50

0 0 1 2 3 4 5

Time (Hours)

1 Figure 5.32: 1hr UH for Ghagra sub-watershed GSW5 .

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180 1hr UH GSW25 (GIUH)

160 1hr UH GSW25 (NRCS)

140

120

100

80

Discharge(Cumec) 60

40

20

0 0 0.5 1 1.5 2 2.5 3 3.5 4

Time (Hours)

2 Figure 5.33: 1hr UH for Ghagra sub-watershed GSW5 .

120 1hr UH GSW14 (GIUH)

100 1hr UH GSW14 (NRCS)

80

60

Discharge(Cumec) 40

20

0 0 1 2 3 4 5 6

Time (Hours)

1 Figure 5.34: 1hr UH for Ghagra sub-watershed GSW4 .

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90 1hr UH GSW24 (GIUH)

80 1hr UH GSW24 (NRCS)

70

60

50

40

Discharge(Cumec) 30

20

10

0 0 0.5 1 1.5 2 2.5

Time (Hours)

2 Figure 5.35: 1hr UH for Ghagra sub-watershed GSW4 .

20

18 1 hr UH GSW13 (GIUH)

16 1 hr UH GSW13 (NRCS)

14

12

10

8 Discharge(Cumec) 6

4

2

0 0 0.5 1 1.5 2 2.5 3 3.5

Time (Hours)

1 Figure 5.36: 1hr UH for Ghagra sub-watershed GSW3 .

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14 1hr UH GSW23 (NRCS) 12 1 hr UH GSW23 (GIUH)

10

8

6 Discharge(Cumec) 4

2

0 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6

Time (Hours)

2 Figure 5.37: 1hr UH for Ghagra sub-watershed GSW3 .

20 1hr UH GSW33 (GIUH) 18 1hr UH GSW33 (NRCS)

16

14

12

10

8 Discharge(Cumec) 6

4

2

0 0 0.5 1 1.5 2 2.5 3 3.5

Time (Hours)

3 Figure 5.38: 1hr UH for Ghagra sub-watershed GSW3 .

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35 1hr UH GSW43 (NRCS)

30 1 hr UH GSW43 (GIUH)

25

20

15 Discharge(Cumec) 10

5

0 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6

Time (Hours)

4 Figure 5.39: 1hr UH for Ghagra sub-watershed GSW3 .

Table -5.5: Unit Hydrograph characteristics for the sub-watersheds.

Watersheds Time to peak Peak discharge Base time

tb  t  Q  p p hrs 

hrs  m3 / s  GIUH NRCS GIUH NRCS GIUH NRCS

1 1.6 1.0 257.78 352.68 4.1 2.8 MSW5 2 1.4 0.9 125.20 175.28 3.6 2.3 MSW5 3 1.1 1.0 177.11 153.37 2.5 2.6 MSW5 1 1.0 0.5 13.32 19.00 1.9 1.5 MSW3 1 1.7 1.4 214.91 241.08 4.6 3.7 GSW5 2 1.4 1.4 167.53 136.93 3.5 3.6 GSW5 1 2.0 1.2 75.81 113.33 5.5 3.4 GSW4 2 1.0 0.5 56.89 84.30 2.1 1.4 GSW4 1 1.3 0.7 12.23 17.87 3.2 2.0 GSW3

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2 0.5 0.3 8.23 11.70 1.5 0.9 GSW3 3 1.2 0.8 16.09 18.11 3.0 2.3 GSW3 4 0.5 0.4 20.33 24.95 1.5 0.8 GSW3 5.1 Routing sub-watershed UHs

Sub-watershed UHs derived using GIUH and NRCS techniques are routed by using nonlinear kinematic wave model to the respective main watershed outlet and superimposed with local flows to develop UH for the watersheds. Values for the parameters  and  required for using nonlinear kinematic model are estimated using flow area and corresponding discharge data series for a section. On the basis of maximum top width Wmax  and maximum flow depth

Ymax  and assuming a parabolic channel section a set of values for the flow area,

Ai and corresponding discharge, Qi are computed. Observed maximum top width and maximum depth for the sub-watershed channel sections in the study sub-watersheds are listed in Table 5.6. Manning’s roughness coefficients, n for the reaches are determined using field information, available soil maps and topographic maps etc. n values selected for different channel sections is also

given in Table 5.6. Derived values for Ai , and Qi for a section are used to estimate routing parameters  and  by applying simple nonlinear regression technique. Reach length and estimated routing parameters  and  are listed in Table 5.7.

Table 5.6 : Channel characteristics and parameters.

Sub- Manning Average Maximum top Maximum watersheds Roughness channel Width depth Coefficient Slope Wmax  Ymax  n  So  m  m  m/ m 

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1 MSW5 0.034 0.337 86.50 4.30

2 MSW5 0.034 0.273 36.10 6.10

3 MSW5 0.030 0.095 59.50 8.55 1 MSW3 0.020 0.084 20.56 3.1 1 GSW5 0.034 0.380 48.40 5.51 2 GSW5 0.034 0.350 48.38 5.00 1 GSW4 0.034 0.400 30.20 7.40 2 GSW4 0.020 0.254 27.50 4.00 1 GSW3 0.020 0.080 5.60 1.53 2 GSW3 0.020 0.071 5.10 1.01 3 GSW3 0.020 0.074 18.60 4.14 4 GSW3 0.020 0.062 14.30 3.61

Table-5.7: Routing parameters for sub-watersheds.

watersheds parameters Reach length

    x  km 

1 0.280 0.750 14.589 MSW5 2 MSW5 0.280 0.750 14.589 3 0.321 0.750 0.929 MSW5 1 MSW3 0.246 0.750 11.191 1 GSW5 0.230 0.750 19.784

2 GSW5 0.232 0.750 19.784 1 0.189 0.750 0.023 GSW4

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2 0.164 0.750 12.794 GSW4 1 0.097 0.750 17.692 GSW3 2 0.250 0.750 13.611 GSW3 3 0.242 0.750 11.227 GSW3 4 .0255 0.750 1.245 GSW3

Using values for the routing parameter,  and  for a reach length, x  the sub-watershed UHs are routed to the respective main outlet. To estimate

j1 Qt1 initial value for the variable is required, in the present case initial estimate

j1 j1 for Qt1 is taken as the estimated value for Qt , the value of the variable in the previous time step. The resulted UHs are then superimposed to derive the respective UH for the watersheds. Figures 5.40 and Figures 5.41 shows the derived 1hr UH for Madhura and Ghagra watersheds using GIUH and NRCS techniques. Morphological parameters for all sub basins are listed in the table 5.8:

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Table-5.8: Morphological parameters and IUH Characteristics of subbasins

Hydraulic t V q q A t b flow length Slope R R R t (hrs) p p b (triangular (m/s) (km) A B L p (-hrs) (Cumec) (Sq. km) (hrs) (m) based) 퐿휔

GHAGRA 48930.00 0.10 4.20 19.78 3.90 3.64 2.02 1.53 0.38 427.64 409.39 5.32 4.08

MADHURA 52609.00 0.28 6.39 14.59 4.31 3.83 2.13 0.71 0.79 858.44 389.43 2.52 1.89

CHIRI 49881.00 0.23 5.85 11.65 3.82 3.50 1.91 0.65 0.87 1057.39 438.12 2.30 1.75

JIRI 103240.00 0.29 7.56 48.09 4.56 4.21 2.44 1.91 0.30 884.39 1052.85 6.61 5.09

KATAKHAL 129880.00 0.11 5.49 57.43 4.35 4.10 2.41 3.19 0.18 763.60 1504.68 10.95 8.52

JATINGA 55390.00 0.35 7.05 22.93 4.01 4.90 3.09 1.04 0.65 675.50 371.86 3.06 2.78

SONAI 95212.00 0.07 4.30 15.98 3.50 3.80 1.93 1.33 0.47 633.14 488.25 4.28 3.56

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800 1hr UH Madhura (R-GIUH) 700 1hr UH Madhura (R-NRCS)

600

500

400

300 Discharge(Cumec)

200

100

0 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 Time (Hours)

Figure -5.40: 1hr UH for Machura watershed.

600

500 1hr UH GSW (R-GIUH)

1hr UH GSW (R-NRCS) 400

300 Discharge(Cumec) 200

100

0 0 1 2 3 4 5 6 Time (Hours)

Figure -5.41: 1hr UH for Ghagra watershed

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Table5.9: 1hr UH ordinates for Chiri subbasin.

Time GIUH GIUH S-curve S-curve lagged by 1hr UH (Hours) ordinate lagged SUM/2 addition ordinate 10x0.1 hr ordinate 0 0.00 0.00 0.00 0.00

0.1 151.06 0.00 75.53 0.00 75.53 7.55

0.2 302.11 151.06 226.58 75.53 302.11 30.21

0.3 453.17 302.11 377.64 302.11 679.75 67.98

0.4 604.22 453.17 528.70 679.75 1208.45 120.84

0.5 755.28 604.22 679.75 1208.45 1888.20 188.82

0.6 906.33 755.28 830.81 1888.20 2719.00 271.90

0.7 1057.39 906.33 981.86 2719.00 3700.87 370.09

0.8 991.36 1057.39 1024.38 3700.87 4725.24 472.52

0.9 925.28 991.36 958.32 4725.24 5683.56 568.36

1 859.20 925.28 892.24 5683.56 6575.80 0.00 657.58

1.1 793.12 859.20 826.16 6575.80 7401.96 75.53 732.64

1.2 727.04 793.12 760.08 7401.96 8162.04 302.11 785.99

1.3 660.96 727.04 694.00 8162.04 8856.04 679.75 817.63

1.4 594.88 660.96 627.92 8856.04 9483.96 1208.45 827.55

1.5 528.80 594.88 561.84 9483.96 10045.80 1888.20 815.76

1.6 462.72 528.80 495.76 10045.80 10541.56 2719.00 782.26

1.7 396.64 462.72 429.68 10541.56 10971.24 3700.87 727.04

1.8 330.56 396.64 363.60 10971.24 11334.84 4725.24 660.96

1.9 264.48 330.56 297.52 11334.84 11632.36 5683.56 594.88

2 198.40 264.48 231.44 11632.36 11863.80 6575.80 528.80

2.1 132.32 198.40 165.36 11863.80 12029.16 7401.96 462.72

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2.2 66.24 132.32 99.28 12029.16 12128.44 8162.04 396.64

2.3 0.16 66.24 33.20 12128.44 12161.64 8856.04 330.56

2.4 0.16 0.08 12161.64 12161.72 9483.96 267.78

2.5 12161.72 12161.72 10045.80 211.59

2.6 12161.72 12161.72 10541.56 162.02

2.7 12161.72 12161.72 10971.24 119.05

2.8 12161.72 12161.72 11334.84 82.69

2.9 12161.72 12161.72 11632.36 52.94

3 12161.72 12161.72 11863.80 29.79

3.1 12161.72 12161.72 12029.16 13.26

3.2 12161.72 12161.72 12128.44 3.33

3.3 12161.72 12161.72 12161.64 0.01

3.4 12161.72 12161.72 12161.72 0.00

Nov- 2013: P. Choudhury-NIT Silchar, Assam153

Flood Damage Mitigation: Report

900.00

800.00 1hr UH Chiri 700.00

600.00

500.00

400.00

300.00 Discharge (cumec) Discharge

200.00

100.00

0.00 0 1 2 3 4 Time (hours)

Figure: 5.42:1hr UH ordinates for Chiri subbasin

Table-5.10: 1hr UH ordinates for Jiri subbasin.

Time GIUH GIUH S-curve S-curve lagged by 1hr UH (Hours) ordinate lagged SUM/2 addition ordinate 10x0.1 hr ordinate 0 0.00 0.00 0.00 0.00

0.1 46.55 0.00 23.27 0.00 23.27 2.33

0.2 93.09 46.55 69.82 23.27 93.09 9.31

0.3 139.64 93.09 116.37 93.09 209.46 20.95

0.4 186.19 139.64 162.91 209.46 372.37 37.24

0.5 232.73 186.19 209.46 372.37 581.83 58.18

0.6 279.28 232.73 256.01 581.83 837.84 83.78

Nov- 2013: P. Choudhury-NIT Silchar, Assam154

Flood Damage Mitigation: Report

0.7 325.83 279.28 302.55 837.84 1140.39 114.04

0.8 372.37 325.83 349.10 1140.39 1489.49 148.95

0.9 418.92 372.37 395.65 1489.49 1885.14 188.51

1 465.47 418.92 442.19 1885.14 2327.33 0.00 232.73

1.1 512.01 465.47 488.74 2327.33 2816.07 23.27 279.28

1.2 558.56 512.01 535.29 2816.07 3351.36 93.09 325.83

1.3 605.11 558.56 581.83 3351.36 3933.19 209.46 372.37

1.4 651.65 605.11 628.38 3933.19 4561.57 372.37 418.92

1.5 698.20 651.65 674.93 4561.57 5236.50 581.83 465.47

1.6 744.75 698.20 721.47 5236.50 5957.97 837.84 512.01

1.7 791.29 744.75 768.02 5957.97 6725.99 1140.39 558.56

1.8 837.84 791.29 814.57 6725.99 7540.55 1489.49 605.11

1.9 884.39 837.84 861.11 7540.55 8401.67 1885.14 651.65

2 864.80 884.39 874.59 8401.67 9276.26 2327.33 694.89

2.1 845.99 864.80 855.40 9276.26 10131.66 2816.07 731.56

2.2 827.18 845.99 836.59 10131.66 10968.24 3351.36 761.69

2.3 808.37 827.18 817.78 10968.24 11786.02 3933.19 785.28

2.4 789.56 808.37 798.97 11786.02 12584.98 4561.57 802.34

2.5 770.75 789.56 780.16 12584.98 13365.14 5236.50 812.86

2.6 751.94 770.75 761.35 13365.14 14126.48 5957.97 816.85

2.7 733.13 751.94 742.54 14126.48 14869.02 6725.99 814.30

2.8 714.32 733.13 723.73 14869.02 15592.74 7540.55 805.22

2.9 695.51 714.32 704.92 15592.74 16297.66 8401.67 789.60

3 676.70 695.51 686.11 16297.66 16983.76 9276.26 770.75

Nov- 2013: P. Choudhury-NIT Silchar, Assam155

Flood Damage Mitigation: Report

3.1 657.89 676.70 667.30 16983.76 17651.06 10131.66 751.94

3.2 639.08 657.89 648.49 17651.06 18299.54 10968.24 733.13

3.3 620.27 639.08 629.68 18299.54 18929.22 11786.02 714.32

3.4 601.46 620.27 610.87 18929.22 19540.08 12584.98 695.51

3.5 582.65 601.46 592.06 19540.08 20132.14 13365.14 676.70

3.6 563.84 582.65 573.25 20132.14 20705.38 14126.48 657.89

3.7 545.03 563.84 554.44 20705.38 21259.82 14869.02 639.08

3.8 526.22 545.03 535.63 21259.82 21795.44 15592.74 620.27

3.9 507.41 526.22 516.82 21795.44 22312.26 16297.66 601.46

4 488.60 507.41 498.01 22312.26 22810.26 16983.76 582.65

4.1 469.79 488.60 479.20 22810.26 23289.46 17651.06 563.84

4.2 450.98 469.79 460.39 23289.46 23749.84 18299.54 545.03

4.3 432.17 450.98 441.58 23749.84 24191.42 18929.22 526.22

4.4 413.36 432.17 422.77 24191.42 24614.18 19540.08 507.41

4.5 394.55 413.36 403.96 24614.18 25018.14 20132.14 488.60

4.6 375.74 394.55 385.15 25018.14 25403.28 20705.38 469.79

4.7 356.93 375.74 366.34 25403.28 25769.62 21259.82 450.98

4.8 338.12 356.93 347.53 25769.62 26117.14 21795.44 432.17

4.9 319.31 338.12 328.72 26117.14 26445.86 22312.26 413.36

5 300.50 319.31 309.91 26445.86 26755.76 22810.26 394.55

5.1 281.69 300.50 291.10 26755.76 27046.86 23289.46 375.74

5.2 262.88 281.69 272.29 27046.86 27319.14 23749.84 356.93

5.3 244.07 262.88 253.48 27319.14 27572.62 24191.42 338.12

5.4 225.26 244.07 234.67 27572.62 27807.28 24614.18 319.31

Nov- 2013: P. Choudhury-NIT Silchar, Assam156

Flood Damage Mitigation: Report

5.5 206.45 225.26 215.86 27807.28 28023.14 25018.14 300.50

5.6 187.64 206.45 197.05 28023.14 28220.18 25403.28 281.69

5.7 168.83 187.64 178.24 28220.18 28398.42 25769.62 262.88

5.8 150.02 168.83 159.43 28398.42 28557.84 26117.14 244.07

5.9 131.21 150.02 140.62 28557.84 28698.46 26445.86 225.26

6 112.40 131.21 121.81 28698.46 28820.26 26755.76 206.45

6.1 93.59 112.40 103.00 28820.26 28923.26 27046.86 187.64

6.2 74.78 93.59 84.19 28923.26 29007.44 27319.14 168.83

6.3 55.97 74.78 65.38 29007.44 29072.82 27572.62 150.02

6.4 37.16 55.97 46.57 29072.82 29119.38 27807.28 131.21

6.5 18.35 37.16 27.76 29119.38 29147.14 28023.14 112.40

6.6 0.00 18.35 9.18 29147.14 29156.31 28220.18 93.61

6.7 0.00 0.00 29156.31 29156.31 28398.42 75.79

6.8 29156.31 29156.31 28557.84 59.85

6.9 29156.31 29156.31 28698.46 45.79

7 29156.31 29156.31 28820.26 33.61

7.1 29156.31 29156.31 28923.26 23.31

7.2 29156.31 29156.31 29007.44 14.89

7.3 29156.31 29156.31 29072.82 8.35

7.4 29156.31 29156.31 29119.38 3.69

7.5 29156.31 29156.31 29147.14 0.92

7.6 29156.31 29156.31 29156.31 0.00

Nov- 2013: P. Choudhury-NIT Silchar, Assam157

Flood Damage Mitigation: Report

900.00

800.00

700.00 1hr UH Jiri

600.00

500.00

400.00

Discharge (cumec) Discharge 300.00

200.00

100.00

0.00 0 1 2 3 4 5 6 7 8 Time (hours)

Figure-5.431hr UH ordinates for Jiri subbasin

Table:5.11 1hr UH ordinates for Jatinga subbasin.

Time GIUH GIUH S-curve S-curve lagged by 1hr UH (Hours) ordinate lagged SUM/2 addition ordinate 10x0.1 hr ordinate 0 0.00 0.00 0.00 0.00

0.1 46.55 0.00 23.27 0.00 23.27 2.33

0.2 93.09 46.55 69.82 23.27 93.09 9.31

0.3 139.64 93.09 116.37 93.09 209.46 20.95

0.4 186.19 139.64 162.91 209.46 372.37 37.24

0.5 232.73 186.19 209.46 372.37 581.83 58.18

Nov- 2013: P. Choudhury-NIT Silchar, Assam158

Flood Damage Mitigation: Report

0.6 279.28 232.73 256.01 581.83 837.84 83.78

0.7 325.83 279.28 302.55 837.84 1140.39 114.04

0.8 372.37 325.83 349.10 1140.39 1489.49 148.95

0.9 418.92 372.37 395.65 1489.49 1885.14 188.51

1 465.47 418.92 442.19 1885.14 2327.33 0.00 232.73

1.1 512.01 465.47 488.74 2327.33 2816.07 23.27 279.28

1.2 558.56 512.01 535.29 2816.07 3351.36 93.09 325.83

1.3 605.11 558.56 581.83 3351.36 3933.19 209.46 372.37

1.4 651.65 605.11 628.38 3933.19 4561.57 372.37 418.92

1.5 698.20 651.65 674.93 4561.57 5236.50 581.83 465.47

1.6 744.75 698.20 721.47 5236.50 5957.97 837.84 512.01

1.7 791.29 744.75 768.02 5957.97 6725.99 1140.39 558.56

1.8 837.84 791.29 814.57 6725.99 7540.55 1489.49 605.11

1.9 884.39 837.84 861.11 7540.55 8401.67 1885.14 651.65

2 864.80 884.39 874.59 8401.67 9276.26 2327.33 694.89

2.1 845.99 864.80 855.40 9276.26 10131.66 2816.07 731.56

2.2 827.18 845.99 836.59 10131.66 10968.24 3351.36 761.69

2.3 808.37 827.18 817.78 10968.24 11786.02 3933.19 785.28

2.4 789.56 808.37 798.97 11786.02 12584.98 4561.57 802.34

2.5 770.75 789.56 780.16 12584.98 13365.14 5236.50 812.86

2.6 751.94 770.75 761.35 13365.14 14126.48 5957.97 816.85

2.7 733.13 751.94 742.54 14126.48 14869.02 6725.99 814.30

2.8 714.32 733.13 723.73 14869.02 15592.74 7540.55 805.22

2.9 695.51 714.32 704.92 15592.74 16297.66 8401.67 789.60

Nov- 2013: P. Choudhury-NIT Silchar, Assam159

Flood Damage Mitigation: Report

3 676.70 695.51 686.11 16297.66 16983.76 9276.26 770.75

3.1 657.89 676.70 667.30 16983.76 17651.06 10131.66 751.94

3.2 639.08 657.89 648.49 17651.06 18299.54 10968.24 733.13

3.3 620.27 639.08 629.68 18299.54 18929.22 11786.02 714.32

3.4 601.46 620.27 610.87 18929.22 19540.08 12584.98 695.51

3.5 582.65 601.46 592.06 19540.08 20132.14 13365.14 676.70

3.6 563.84 582.65 573.25 20132.14 20705.38 14126.48 657.89

3.7 545.03 563.84 554.44 20705.38 21259.82 14869.02 639.08

3.8 526.22 545.03 535.63 21259.82 21795.44 15592.74 620.27

3.9 507.41 526.22 516.82 21795.44 22312.26 16297.66 601.46

4 488.60 507.41 498.01 22312.26 22810.26 16983.76 582.65

4.1 469.79 488.60 479.20 22810.26 23289.46 17651.06 563.84

4.2 450.98 469.79 460.39 23289.46 23749.84 18299.54 545.03

4.3 432.17 450.98 441.58 23749.84 24191.42 18929.22 526.22

4.4 413.36 432.17 422.77 24191.42 24614.18 19540.08 507.41

4.5 394.55 413.36 403.96 24614.18 25018.14 20132.14 488.60

4.6 375.74 394.55 385.15 25018.14 25403.28 20705.38 469.79

4.7 356.93 375.74 366.34 25403.28 25769.62 21259.82 450.98

4.8 338.12 356.93 347.53 25769.62 26117.14 21795.44 432.17

4.9 319.31 338.12 328.72 26117.14 26445.86 22312.26 413.36

5 300.50 319.31 309.91 26445.86 26755.76 22810.26 394.55

5.1 281.69 300.50 291.10 26755.76 27046.86 23289.46 375.74

5.2 262.88 281.69 272.29 27046.86 27319.14 23749.84 356.93

5.3 244.07 262.88 253.48 27319.14 27572.62 24191.42 338.12

Nov- 2013: P. Choudhury-NIT Silchar, Assam160

Flood Damage Mitigation: Report

5.4 225.26 244.07 234.67 27572.62 27807.28 24614.18 319.31

5.5 206.45 225.26 215.86 27807.28 28023.14 25018.14 300.50

5.6 187.64 206.45 197.05 28023.14 28220.18 25403.28 281.69

5.7 168.83 187.64 178.24 28220.18 28398.42 25769.62 262.88

5.8 150.02 168.83 159.43 28398.42 28557.84 26117.14 244.07

5.9 131.21 150.02 140.62 28557.84 28698.46 26445.86 225.26

6 112.40 131.21 121.81 28698.46 28820.26 26755.76 206.45

6.1 93.59 112.40 103.00 28820.26 28923.26 27046.86 187.64

6.2 74.78 93.59 84.19 28923.26 29007.44 27319.14 168.83

6.3 55.97 74.78 65.38 29007.44 29072.82 27572.62 150.02

6.4 37.16 55.97 46.57 29072.82 29119.38 27807.28 131.21

6.5 18.35 37.16 27.76 29119.38 29147.14 28023.14 112.40

6.6 0.00 18.35 9.18 29147.14 29156.31 28220.18 93.61

6.7 0.00 0.00 29156.31 29156.31 28398.42 75.79

6.8 29156.31 29156.31 28557.84 59.85

6.9 29156.31 29156.31 28698.46 45.79

7 29156.31 29156.31 28820.26 33.61

7.1 29156.31 29156.31 28923.26 23.31

7.2 29156.31 29156.31 29007.44 14.89

7.3 29156.31 29156.31 29072.82 8.35

7.4 29156.31 29156.31 29119.38 3.69

7.5 29156.31 29156.31 29147.14 0.92

7.6 29156.31 29156.31 29156.31 0.00

Nov- 2013: P. Choudhury-NIT Silchar, Assam161

Flood Damage Mitigation: Report

600.00

500.00

400.00 1hr UH Jatinga

300.00

200.00 Discharge (cumec) Discharge

100.00

0.00 0.00 1.00 2.00 3.00 4.00 5.00 Time (hours)

Figure: 5.44 1hr UH ordinates for Jhatinga subbasin

Table:5.12: 1hr UH ordinates for Sonai subbasin.

Time GIUH GIUH S-curve S-curve lagged by 1hrUH (Hours) ordinate lagged SUM/2 addition ordinate 10x0.1 hr ordinate 0.00 0.00 0.00 0.00 0.00

0.10 48.70 0.00 24.35 0.00 24.35 2.44

0.20 97.41 48.70 73.05 24.35 97.41 9.74

0.30 146.11 97.41 121.76 97.41 219.16 21.92

0.40 194.81 146.11 170.46 219.16 389.62 38.96

0.50 243.51 194.81 219.16 389.62 608.79 60.88

0.60 292.22 243.51 267.87 608.79 876.65 87.67

0.70 340.92 292.22 316.57 876.65 1193.22 119.32

Nov- 2013: P. Choudhury-NIT Silchar, Assam162

Flood Damage Mitigation: Report

0.80 389.62 340.92 365.27 1193.22 1558.49 155.85

0.90 438.33 389.62 413.97 1558.49 1972.47 197.25

1.00 487.03 438.33 462.68 1972.47 2435.15 0.00 243.51

1.10 535.73 487.03 511.38 2435.15 2946.53 24.35 292.22

1.20 584.43 535.73 560.08 2946.53 3506.61 97.41 340.92

1.30 633.14 584.43 608.79 3506.61 4115.40 219.16 389.62

1.40 612.10 633.14 622.62 4115.40 4738.01 389.62 434.84

1.50 591.00 612.10 601.55 4738.01 5339.56 608.79 473.08

1.60 569.90 591.00 580.45 5339.56 5920.01 876.65 504.34

1.70 548.80 569.90 559.35 5920.01 6479.36 1193.22 528.61

1.80 527.70 548.80 538.25 6479.36 7017.61 1558.49 545.91

1.90 506.60 527.70 517.15 7017.61 7534.76 1972.47 556.23

2.00 485.50 506.60 496.05 7534.76 8030.81 2435.15 559.57

2.10 464.40 485.50 474.95 8030.81 8505.76 2946.53 555.92

2.20 443.30 464.40 453.85 8505.76 8959.61 3506.61 545.30

2.30 422.20 443.30 432.75 8959.61 9392.36 4115.40 527.70

2.40 401.10 422.20 411.65 9392.36 9804.01 4738.01 506.60

2.50 380.00 401.10 390.55 9804.01 10194.56 5339.56 485.50

2.60 358.90 380.00 369.45 10194.56 10564.01 5920.01 464.40

2.70 337.80 358.90 348.35 10564.01 10912.36 6479.36 443.30

2.80 316.70 337.80 327.25 10912.36 11239.61 7017.61 422.20

2.90 295.60 316.70 306.15 11239.61 11545.76 7534.76 401.10

3.00 274.50 295.60 285.05 11545.76 11830.81 8030.81 380.00

3.10 253.40 274.50 263.95 11830.81 12094.76 8505.76 358.90

Nov- 2013: P. Choudhury-NIT Silchar, Assam163

Flood Damage Mitigation: Report

3.20 232.30 253.40 242.85 12094.76 12337.61 8959.61 337.80

3.30 211.20 232.30 221.75 12337.61 12559.36 9392.36 316.70

3.40 190.10 211.20 200.65 12559.36 12760.01 9804.01 295.60

3.50 169.00 190.10 179.55 12760.01 12939.56 10194.56 274.50

3.60 147.90 169.00 158.45 12939.56 13098.01 10564.01 253.40

3.70 126.80 147.90 137.35 13098.01 13235.36 10912.36 232.30

3.80 105.70 126.80 116.25 13235.36 13351.61 11239.61 211.20

3.90 84.60 105.70 95.15 13351.61 13446.76 11545.76 190.10

4.00 63.50 84.60 74.05 13446.76 13520.81 11830.81 169.00

4.10 42.40 63.50 52.95 13520.81 13573.76 12094.76 147.90

4.20 21.30 42.40 31.85 13573.76 13605.61 12337.61 126.80

4.30 0.20 21.30 10.75 13605.61 13616.36 12559.36 105.70

4.40 0.00 0.20 0.10 13616.36 13616.46 12760.01 85.64

4.50 0.00 0.00 13616.46 13616.46 12939.56 67.69

4.60 13616.46 13616.46 13098.01 51.84

4.70 13616.46 13616.46 13235.36 38.11

4.80 13616.46 13616.46 13351.61 26.48

4.90 13616.46 13616.46 13446.76 16.97

5.00 13616.46 13616.46 13520.81 9.56

5.10 13616.46 13616.46 13573.76 4.27

5.20 13616.46 13616.46 13605.61 1.09

5.30 13616.46 13616.46 13616.36 0.01

5.40 13616.46 13616.46 13616.46 0.00

Nov- 2013: P. Choudhury-NIT Silchar, Assam164

Flood Damage Mitigation: Report

Figure 5.45: 1hr UH ordinates for Sonai Subbasin

Table 5.13: 1hr UH ordinates for Katakhal subbasin.

Time GIUH GIUH S-curve S-curve lagged by (Hours) ordinate lagged SUM/2 addition ordinate 10x0.1 hr 1hr UH ordinate 0 0.00 0.00 0.00 0.00

0.1 23.86 0.00 11.93 0.00 11.93 1.19

0.2 47.72 23.86 35.79 11.93 47.72 4.77

0.3 71.59 47.72 59.66 47.72 107.38 10.74

0.4 95.45 71.59 83.52 107.38 190.90 19.09

0.5 119.31 95.45 107.38 190.90 298.28 29.83

0.6 143.17 119.31 131.24 298.28 429.52 42.95

0.7 167.04 143.17 155.11 429.52 584.63 58.46

0.8 190.90 167.04 178.97 584.63 763.60 76.36

Nov- 2013: P. Choudhury-NIT Silchar, Assam165

Flood Damage Mitigation: Report

0.9 214.76 190.90 202.83 763.60 966.43 96.64

1 238.62 214.76 226.69 966.43 1193.12 0.00 119.31

1.1 262.49 238.62 250.56 1193.12 1443.67 11.93 143.17

1.2 286.35 262.49 274.42 1443.67 1718.09 47.72 167.04

1.3 310.21 286.35 298.28 1718.09 2016.37 107.38 190.90

1.4 334.07 310.21 322.14 2016.37 2338.51 190.90 214.76

1.5 357.94 334.07 346.00 2338.51 2684.52 298.28 238.62

1.6 381.80 357.94 369.87 2684.52 3054.39 429.52 262.49

1.7 405.66 381.80 393.73 3054.39 3448.11 584.63 286.35

1.8 429.52 405.66 417.59 3448.11 3865.71 763.60 310.21

1.9 453.39 429.52 441.45 3865.71 4307.16 966.43 334.07

2 477.25 453.39 465.32 4307.16 4772.48 1193.12 357.94

2.1 501.11 477.25 489.18 4772.48 5261.66 1443.67 381.80

2.2 524.97 501.11 513.04 5261.66 5774.70 1718.09 405.66

2.3 548.83 524.97 536.90 5774.70 6311.60 2016.37 429.52

2.4 572.70 548.83 560.77 6311.60 6872.37 2338.51 453.39

2.5 596.56 572.70 584.63 6872.37 7457.00 2684.52 477.25

2.6 620.42 596.56 608.49 7457.00 8065.49 3054.39 501.11

2.7 644.28 620.42 632.35 8065.49 8697.84 3448.11 524.97

2.8 668.15 644.28 656.22 8697.84 9354.05 3865.71 548.83

2.9 692.01 668.15 680.08 9354.05 10034.13 4307.16 572.70

3 715.87 692.01 703.94 10034.13 10738.07 4772.48 596.56

3.1 739.73 715.87 727.80 10738.07 11465.88 5261.66 620.42

3.2 763.60 739.73 751.67 11465.88 12217.54 5774.70 644.28

Nov- 2013: P. Choudhury-NIT Silchar, Assam166

Flood Damage Mitigation: Report

3.3 752.77 763.60 758.18 12217.54 12975.73 6311.60 666.41

3.4 742.86 752.77 747.81 12975.73 13723.54 6872.37 685.12

3.5 732.94 742.86 737.90 13723.54 14461.44 7457.00 700.44

3.6 723.02 732.94 727.98 14461.44 15189.42 8065.49 712.39

3.7 713.11 723.02 718.07 15189.42 15907.49 8697.84 720.96

3.8 703.19 713.11 708.15 15907.49 16615.64 9354.05 726.16

3.9 693.28 703.19 698.23 16615.64 17313.87 10034.13 727.97

4 683.36 693.28 688.32 17313.87 18002.19 10738.07 726.41

4.1 673.44 683.36 678.40 18002.19 18680.59 11465.88 721.47

4.2 663.53 673.44 668.49 18680.59 19349.08 12217.54 713.15

4.3 653.61 663.53 658.57 19349.08 20007.65 12975.73 703.19

4.4 643.70 653.61 648.65 20007.65 20656.30 13723.54 693.28

4.5 633.78 643.70 638.74 20656.30 21295.04 14461.44 683.36

4.6 623.86 633.78 628.82 21295.04 21923.86 15189.42 673.44

4.7 613.95 623.86 618.91 21923.86 22542.77 15907.49 663.53

4.8 604.03 613.95 608.99 22542.77 23151.76 16615.64 653.61

4.9 594.12 604.03 599.07 23151.76 23750.83 17313.87 643.70

5 584.20 594.12 589.16 23750.83 24339.99 18002.19 633.78

5.1 574.28 584.20 579.24 24339.99 24919.23 18680.59 623.86

5.2 564.37 574.28 569.33 24919.23 25488.56 19349.08 613.95

5.3 554.45 564.37 559.41 25488.56 26047.97 20007.65 604.03

5.4 544.54 554.45 549.49 26047.97 26597.46 20656.30 594.12

5.5 534.62 544.54 539.58 26597.46 27137.04 21295.04 584.20

5.6 524.70 534.62 529.66 27137.04 27666.70 21923.86 574.28

Nov- 2013: P. Choudhury-NIT Silchar, Assam167

Flood Damage Mitigation: Report

5.7 514.79 524.70 519.75 27666.70 28186.45 22542.77 564.37

5.8 504.87 514.79 509.83 28186.45 28696.28 23151.76 554.45

5.9 494.96 504.87 499.91 28696.28 29196.19 23750.83 544.54

6 485.04 494.96 490.00 29196.19 29686.19 24339.99 534.62

6.1 475.12 485.04 480.08 29686.19 30166.27 24919.23 524.70

6.2 465.21 475.12 470.17 30166.27 30636.44 25488.56 514.79

6.3 455.29 465.21 460.25 30636.44 31096.69 26047.97 504.87

6.4 445.38 455.29 450.33 31096.69 31547.02 26597.46 494.96

6.5 435.46 445.38 440.42 31547.02 31987.44 27137.04 485.04

6.6 425.54 435.46 430.50 31987.44 32417.94 27666.70 475.12

6.7 415.63 425.54 420.59 32417.94 32838.53 28186.45 465.21

6.8 405.71 415.63 410.67 32838.53 33249.20 28696.28 455.29

6.9 395.80 405.71 400.75 33249.20 33649.95 29196.19 445.38

7 385.88 395.80 390.84 33649.95 34040.79 29686.19 435.46

7.1 375.96 385.88 380.92 34040.79 34421.71 30166.27 425.54

7.2 366.05 375.96 371.01 34421.71 34792.72 30636.44 415.63

7.3 356.13 366.05 361.09 34792.72 35153.81 31096.69 405.71

7.4 346.22 356.13 351.17 35153.81 35504.98 31547.02 395.80

7.5 336.30 346.22 341.26 35504.98 35846.24 31987.44 385.88

7.6 326.38 336.30 331.34 35846.24 36177.58 32417.94 375.96

7.7 316.47 326.38 321.43 36177.58 36499.01 32838.53 366.05

7.8 306.55 316.47 311.51 36499.01 36810.52 33249.20 356.13

7.9 296.64 306.55 301.59 36810.52 37112.11 33649.95 346.22

8 286.72 296.64 291.68 37112.11 37403.79 34040.79 336.30

Nov- 2013: P. Choudhury-NIT Silchar, Assam168

Flood Damage Mitigation: Report

8.1 276.80 286.72 281.76 37403.79 37685.55 34421.71 326.38

8.2 266.89 276.80 271.85 37685.55 37957.40 34792.72 316.47

8.3 256.97 266.89 261.93 37957.40 38219.33 35153.81 306.55

8.4 247.06 256.97 252.01 38219.33 38471.34 35504.98 296.64

8.5 237.14 247.06 242.10 38471.34 38713.44 35846.24 286.72

8.6 227.22 237.14 232.18 38713.44 38945.62 36177.58 276.80

8.7 217.31 227.22 222.27 38945.62 39167.89 36499.01 266.89

8.8 207.39 217.31 212.35 39167.89 39380.24 36810.52 256.97

8.9 197.48 207.39 202.43 39380.24 39582.67 37112.11 247.06

9 187.56 197.48 192.52 39582.67 39775.19 37403.79 237.14

9.1 177.64 187.56 182.60 39775.19 39957.79 37685.55 227.22

9.2 167.73 177.64 172.69 39957.79 40130.48 37957.40 217.31

9.3 157.81 167.73 162.77 40130.48 40293.25 38219.33 207.39

9.4 147.90 157.81 152.85 40293.25 40446.10 38471.34 197.48

9.5 137.98 147.90 142.94 40446.10 40589.04 38713.44 187.56

9.6 128.06 137.98 133.02 40589.04 40722.06 38945.62 177.64

9.7 118.15 128.06 123.11 40722.06 40845.17 39167.89 167.73

9.8 108.23 118.15 113.19 40845.17 40958.36 39380.24 157.81

9.9 98.32 108.23 103.27 40958.36 41061.63 39582.67 147.90

10 88.40 98.32 93.36 41061.63 41154.99 39775.19 137.98

10.1 78.48 88.40 83.44 41154.99 41238.43 39957.79 128.06

10.2 68.57 78.48 73.53 41238.43 41311.96 40130.48 118.15

10.3 58.65 68.57 63.61 41311.96 41375.57 40293.25 108.23

10.4 48.74 58.65 53.69 41375.57 41429.26 40446.10 98.32

Nov- 2013: P. Choudhury-NIT Silchar, Assam169

Flood Damage Mitigation: Report

10.5 38.82 48.74 43.78 41429.26 41473.04 40589.04 88.40

10.6 28.90 38.82 33.86 41473.04 41506.90 40722.06 78.48

10.7 18.99 28.90 23.95 41506.90 41530.85 40845.17 68.57

10.8 9.07 18.99 14.03 41530.85 41544.88 40958.36 58.65

10.9 0.00 9.07 4.54 41544.88 41549.41 41061.63 48.78

11 0.00 0.00 41549.41 41549.41 41154.99 39.44

11.1 41549.41 41549.41 41238.43 31.10

11.2 41549.41 41549.41 41311.96 23.75

11.3 41549.41 41549.41 41375.57 17.38

11.4 41549.41 41549.41 41429.26 12.02

11.5 41549.41 41549.41 41473.04 7.64

11.6 41549.41 41549.41 41506.90 4.25

11.7 41549.41 41549.41 41530.85 1.86

11.8 41549.41 41549.41 41544.88 0.45

11.9 41549.41 41549.41 41549.41 0.00

12 41549.41 41549.41 41549.41 0.00

Nov- 2013: P. Choudhury-NIT Silchar, Assam170

Flood Damage Mitigation: Report

800.00

700.00

600.00 Series1 500.00

400.00

300.00

Discharge (cumec) Discharge 200.00

100.00

0.00 0 2 4 6 8 10 12 14 Time (hours)

Figure 5.46: 1hr UH ordinates for Katakhal subbasin

Nov- 2013: P. Choudhury-NIT Silchar, Assam171